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Editor’s Choice Articles

Editor’s Choice articles are based on recommendations by the scientific editors of MDPI journals from around the world. Editors select a small number of articles recently published in the journal that they believe will be particularly interesting to readers, or important in the respective research area. The aim is to provide a snapshot of some of the most exciting work published in the various research areas of the journal.

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22 pages, 3156 KB  
Review
Gold Nanoparticles as a Biosensor for Cancer Biomarker Determination
by Chien-Hsiu Li, Ming-Hsien Chan, Yu-Chan Chang and Michael Hsiao
Molecules 2023, 28(1), 364; https://doi.org/10.3390/molecules28010364 - 2 Jan 2023
Cited by 50 | Viewed by 9125
Abstract
Molecular biology applications based on gold nanotechnology have revolutionary impacts, especially in diagnosing and treating molecular and cellular levels. The combination of plasmonic resonance, biochemistry, and optoelectronic engineering has increased the detection of molecules and the possibility of atoms. These advantages have brought [...] Read more.
Molecular biology applications based on gold nanotechnology have revolutionary impacts, especially in diagnosing and treating molecular and cellular levels. The combination of plasmonic resonance, biochemistry, and optoelectronic engineering has increased the detection of molecules and the possibility of atoms. These advantages have brought medical research to the cellular level for application potential. Many research groups are working towards this. The superior analytical properties of gold nanoparticles can not only be used as an effective drug screening instrument for gene sequencing in new drug development but also as an essential tool for detecting physiological functions, such as blood glucose, antigen-antibody analysis, etc. The review introduces the principles of biomedical sensing systems, the principles of nanomaterial analysis applied to biomedicine at home and abroad, and the chemical surface modification of various gold nanoparticles. Full article
(This article belongs to the Special Issue Recent Trends of Functional Nanomaterials for Biomedical and Healthcare Applications)
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13 pages, 1337 KB  
Review
Tyrosinase Inhibitors Naturally Present in Plants and Synthetic Modifications of These Natural Products as Anti-Melanogenic Agents: A Review
by Mubashir Hassan, Saba Shahzadi and Andrzej Kloczkowski
Molecules 2023, 28(1), 378; https://doi.org/10.3390/molecules28010378 - 2 Jan 2023
Cited by 70 | Viewed by 12315
Abstract
Tyrosinase is a key enzyme target to design new chemical ligands against melanogenesis. In the current review, different chemical derivatives are explored which have been used as anti-melanogenic compounds. These are different chemical compounds naturally present in plants and semi-synthetic and synthetic compounds [...] Read more.
Tyrosinase is a key enzyme target to design new chemical ligands against melanogenesis. In the current review, different chemical derivatives are explored which have been used as anti-melanogenic compounds. These are different chemical compounds naturally present in plants and semi-synthetic and synthetic compounds inspired by these natural products, such as kojic acid produced by several species of fungi; arbutin—a glycosylated hydroquinone extracted from the bearberry plant; vanillin—a phenolic aldehyde extracted from the vanilla bean, etc. After enzyme inhibition screening, various chemical compounds showed different therapeutic effects as tyrosinase inhibitors with different values of the inhibition constant and IC50. We show how appropriately designed scaffolds inspired by the structures of natural compounds are used to develop novel synthetic inhibitors. We review the results of numerous studies, which could lead to the development of effective anti-tyrosinase agents with increased efficiency and safety in the near future, with many applications in the food, pharmaceutical and cosmetics industries. Full article
(This article belongs to the Special Issue Natural Product-Inspired Molecules: From Weed to Remedy)
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11 pages, 3282 KB  
Article
Efficient Hydrogen and Oxygen Evolution Catalysis Using 3D-Structured Nickel Phosphosulfide Nanosheets in Alkaline Media
by Lei Lin, Qiang Fu, Junbei Hu, Ran Wang and Xianjie Wang
Molecules 2023, 28(1), 315; https://doi.org/10.3390/molecules28010315 - 30 Dec 2022
Cited by 4 | Viewed by 3299
Abstract
Water electrolysis offers a zero-carbon route to generate renewable energy conversion systems. Herein, a self-supported nickel phosphosulfide nanosheet (NS) electrocatalyst was fabricated at a low temperature on carbon cloth, which was then subjected to Ar etching to enhance its catalytic activity. Etching resulted [...] Read more.
Water electrolysis offers a zero-carbon route to generate renewable energy conversion systems. Herein, a self-supported nickel phosphosulfide nanosheet (NS) electrocatalyst was fabricated at a low temperature on carbon cloth, which was then subjected to Ar etching to enhance its catalytic activity. Etching resulted in better hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performance than other samples, with overpotentials of 103.1 mV (at 10 mA cm−2) and 278.9 mV (at 50 mA cm−2), respectively. The characterization results confirmed that Ar etching created a thin amorphous layer around the NiPS3 NSs, which increased the number of active sites and modulated their electronic structures. These 3D-structured NiPS3 NSs and their subsequent Ar etching process show promise for applications in overall water splitting in alkaline media. Full article
(This article belongs to the Special Issue Advanced Energy Storage Materials and Their Applications)
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18 pages, 13113 KB  
Article
Gaseous- and Condensed-Phase Activities of Some Reactive P- and N-Containing Fire Retardants in Polystyrenes
by Svetlana Tretsiakova-McNally, Aloshy Baby, Paul Joseph, Doris Pospiech, Eileen Schierz, Albena Lederer, Malavika Arun and Gaëlle Fontaine
Molecules 2023, 28(1), 278; https://doi.org/10.3390/molecules28010278 - 29 Dec 2022
Cited by 6 | Viewed by 3062
Abstract
Polystyrene (PS) was modified by covalently binding P-, P-N- and/or N- containing fire-retardant moieties through co- or ter-polymerization reactions of styrene with diethyl(acryloyloxymethyl)phosphonate (DEAMP), diethyl-p-vinylbenzyl phosphonate (DEpVBP), acrylic acid-2-[(diethoxyphosphoryl)methylamino]ethyl ester (ADEPMAE) and maleimide (MI). In the present study, the condensed-phase and [...] Read more.
Polystyrene (PS) was modified by covalently binding P-, P-N- and/or N- containing fire-retardant moieties through co- or ter-polymerization reactions of styrene with diethyl(acryloyloxymethyl)phosphonate (DEAMP), diethyl-p-vinylbenzyl phosphonate (DEpVBP), acrylic acid-2-[(diethoxyphosphoryl)methylamino]ethyl ester (ADEPMAE) and maleimide (MI). In the present study, the condensed-phase and the gaseous-phase activities of the abovementioned fire retardants within the prepared co- and ter-polymers were evaluated for the first time. Pyrolysis–Gas Chromatography/Mass Spectrometry was employed to identify the volatile products formed during the thermal decomposition of the modified polymers. Benzaldehyde, α-methylstyrene, acetophenone, triethyl phosphate and styrene (monomer, dimer and trimer) were detected in the gaseous phase following the thermal cracking of fire-retardant groups and through main chain scissions. In the case of PS modified with ADEPMAE, the evolution of pyrolysis gases was suppressed by possible inhibitory actions of triethyl phosphate in the gaseous phase. The reactive modification of PS by simultaneously incorporating P- (DEAMP or DEpVBP) and N- (MI) monomeric units, in the chains of ter-polymers, resulted in a predominantly condensed-phase mode of action owing to synergistic P and N interactions. The solid-state 31P NMR spectroscopy, Scanning Electron Microscopy/Energy Dispersive Spectroscopy, Inductively-Coupled Plasma/Optical Emission Spectroscopy and X-ray Photoelectron Spectroscopy of char residues, obtained from ter-polymers, confirmed the retention of the phosphorus species in their structures. Full article
(This article belongs to the Special Issue Feature Papers in Materials Chemistry)
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12 pages, 6615 KB  
Article
Low-Temperature Toluene Oxidation on Fe-Containing Modified SBA-15 Materials
by Ivalina Trendafilova, Manuel Ojeda, John M. Andresen, Alenka Ristić, Momtchil Dimitrov, Nataša Novak Tušar, Genoveva Atanasova and Margarita Popova
Molecules 2023, 28(1), 204; https://doi.org/10.3390/molecules28010204 - 26 Dec 2022
Cited by 4 | Viewed by 3097
Abstract
Transition metals as catalysts for total VOC oxidation at low temperatures (150–280 °C) are a big challenge nowadays. Therefore, iron-modified SBA-15, AlSBA-15, and ZrSBA-15 materials with 0.5 to 5.0 wt.% Fe loading were prepared and tested for toluene oxidation. It was found that [...] Read more.
Transition metals as catalysts for total VOC oxidation at low temperatures (150–280 °C) are a big challenge nowadays. Therefore, iron-modified SBA-15, AlSBA-15, and ZrSBA-15 materials with 0.5 to 5.0 wt.% Fe loading were prepared and tested for toluene oxidation. It was found that increasing Fe loading significantly improved the rate of oxidation and lowered the temperature of achieving 100% removal of toluene from above 500 °C for the supports (AlSBA-15 and ZrSBA-15) to below 400 °C for 5FeZrSBA-15. The formation of finely dispersed iron oxide active sites with a particle size less than 5 nm was observed on all the SBA-15, AlSBA-15, and ZrSBA-15 supports. It was found that the surface properties of the mesoporous support due to the addition of Al or Zr predetermined the type of formed iron oxide species and their localization on the support surface. Fe-containing SBA-15 and AlSBA-15 showed activity in total toluene oxidation at higher temperatures (280–450 °C). However, 5 wt. % Fe-containing ZrSBA-15 showed excellent activity in the total oxidation of toluene as a model VOC at lower temperatures (150–380 °C) due to the synergistic effect of Fe-Zr and the presence of accessible and stable Fe2+/Fe3+ active sites. Full article
(This article belongs to the Special Issue Catalysis by Hybrid Materials)
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18 pages, 5435 KB  
Review
Recent Progresses in Solution-Processed Tandem Organic and Quantum Dots Light-Emitting Diodes
by Shu-Guang Meng, Xiao-Zhao Zhu, Dong-Ying Zhou and Liang-Sheng Liao
Molecules 2023, 28(1), 134; https://doi.org/10.3390/molecules28010134 - 23 Dec 2022
Cited by 8 | Viewed by 7112
Abstract
Solution processes have promising advantages of low manufacturing cost and large-scale production, potentially applied for the fabrication of organic and quantum dot light-emitting diodes (OLEDs and QLEDs). To meet the expected lifespan of OLEDs/QLEDs in practical display and lighting applications, tandem architecture by [...] Read more.
Solution processes have promising advantages of low manufacturing cost and large-scale production, potentially applied for the fabrication of organic and quantum dot light-emitting diodes (OLEDs and QLEDs). To meet the expected lifespan of OLEDs/QLEDs in practical display and lighting applications, tandem architecture by connecting multiple light-emitting units (LEUs) through a feasible intermediate connection layer (ICL) is preferred. However, the combination of tandem architecture with solution processes is still limited by the choices of obtainable ICLs due to the unsettled challenges, such as orthogonal solubility, surface wettability, interfacial corrosion, and charge injection. This review focuses on the recent progresses of solution-processed tandem OLEDs and tandem QLEDs, covers the design and fabrication of various ICLs by solution process, and provides suggestions on the future challenges of corresponding materials and devices, which are anticipated to stimulate the exploitation of the emerging light technologies. Full article
(This article belongs to the Special Issue Organic Light-Emitting Diodes 3.0)
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14 pages, 1133 KB  
Article
Possibility of New Active Substrates (ASs) to Be Used to Prevent the Migration of Heavy Metals to the Soil and Water Environments
by Katarzyna Witt, Waldemar Studziński and Daria Bożejewicz
Molecules 2023, 28(1), 94; https://doi.org/10.3390/molecules28010094 - 22 Dec 2022
Viewed by 2238
Abstract
This paper aims to propose an alternative to the known permeable reactive barriers (PRBs). PRB is one of the methods, which is a reactive barrier placed below the ground, to clean up contaminated groundwater. New polymer active substrates (ASs) were used to prevent [...] Read more.
This paper aims to propose an alternative to the known permeable reactive barriers (PRBs). PRB is one of the methods, which is a reactive barrier placed below the ground, to clean up contaminated groundwater. New polymer active substrates (ASs) were used to prevent soil contamination by toxic heavy metals. The active substrates consisted of a mixture of poly(vinyl chloride), Aliquat 336, and bis(2-ethylhexyl)adipate, which was applied to the skeleton material (fiberglass or textile). Aliquat 336 was used as a binding agent for metal ions (Cr(VI), Ni(II), Cu(II), Zn(II), Cd(II), and Pb(II)). In contrast with the PRBs, the ASs (from AS-1 to AS-5) were obtained in a simple way using the pouring method. The obtained ASs could be recycled and reused. The active substrates were used for the binding of various metal ions from aqueous solutions and the examined soil. It was found that the active substrate AS-1 decreased the concentrations of nickel, cadmium, and lead by more than 50% and that of chromium by more than 90% in the aqueous solution. High sorption efficiency for chromium and zinc metals (81% and 66%) with the use of AS-2 was also found, owing to which the migration of metals from soil to water can be limited. In the soil environment, active substrate AS-5 with the addition of a plasticizer showed the greatest effectiveness. This solution resulted in a reduction in each tested metal ion of at least 50%, and reductions in cadmium, lead, and copper of over 70%. Full article
(This article belongs to the Special Issue Innovative Adsorbents for Water Treatment)
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16 pages, 8684 KB  
Review
Mechanisms Involved in the Modification of Textiles by Non-Equilibrium Plasma Treatment
by Gregor Primc, Rok Zaplotnik, Alenka Vesel and Miran Mozetič
Molecules 2022, 27(24), 9064; https://doi.org/10.3390/molecules27249064 - 19 Dec 2022
Cited by 5 | Viewed by 2384
Abstract
Plasma methods are often employed for the desired wettability and soaking properties of polymeric textiles, but the exact mechanisms involved in plasma–textile interactions are yet to be discovered. This review presents the fundamentals of plasma penetration into textiles and illustrates mechanisms that lead [...] Read more.
Plasma methods are often employed for the desired wettability and soaking properties of polymeric textiles, but the exact mechanisms involved in plasma–textile interactions are yet to be discovered. This review presents the fundamentals of plasma penetration into textiles and illustrates mechanisms that lead to the appropriate surface finish of fibers inside the textile. The crucial relations are provided, and the different concepts of low-pressure and atmospheric-pressure discharges useful for the modification of textile’s properties are explained. The atmospheric-pressure plasma sustained in the form of numerous stochastical streamers will penetrate textiles of reasonable porosity, so the reactive species useful for the functionalization of fibers deep inside the textile will be created inside the textile. Low-pressure plasmas sustained at reasonable discharge power will not penetrate into the textile, so the depth of the modified textile is limited by the diffusion of reactive species. Since the charged particles neutralize on the textile surface, the neutral species will functionalize the fibers deep inside the textile when low-pressure plasma is chosen for the treatment of textiles. Full article
(This article belongs to the Special Issue Advances in Textile Materials Chemistry)
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15 pages, 3575 KB  
Article
Electrochemical Characterization and Voltammetric Determination of Methylisothiazolinone on a Boron-Doped Diamond Electrode
by Magdalena Jakubczyk, Slawomir Michalkiewicz, Agata Skorupa and Kinga Krajcarz
Molecules 2022, 27(24), 9013; https://doi.org/10.3390/molecules27249013 - 17 Dec 2022
Viewed by 2989
Abstract
The electrochemical properties of methylisothiazolinone (MIT), the most widely used preservative, were investigated by cyclic (CV) and differential pulse voltammetry (DPV) to develop a new method for its determination. To our knowledge, this is the first demonstration of a voltammetric procedure for the [...] Read more.
The electrochemical properties of methylisothiazolinone (MIT), the most widely used preservative, were investigated by cyclic (CV) and differential pulse voltammetry (DPV) to develop a new method for its determination. To our knowledge, this is the first demonstration of a voltammetric procedure for the determination of MIT on a boron-doped diamond electrode (BDDE) in a citrate–phosphate buffer (C-PB) environment. The anodic oxidation process of methylisothiazolinone, which is the basis of this method, proved to be diffusion-controlled and proceeded with an irreversible two-electron exchange. The radical cations, as unstable primary products, were converted in subsequent chemical reactions to sulfoxides and sulfones, and finally to more stable final products. Performed determinations were based on the DPV technique. A linear calibration curve was obtained in the concentration range from 0.7 to 18.7 mg L−1, with a correlation coefficient of 0.9999. The proposed procedure was accurate and precise, allowing the detection of MIT at a concentration level of 0.24 mg L−1. It successfully demonstrated its suitability for the determination of methylisothiazolinone in household products without the need for any separation steps. The proposed method can serve as an alternative to the prevailing chromatographic determinations of MIT in real samples. Full article
(This article belongs to the Special Issue New Science of Boron Allotropes, Compounds, and Nanomaterials)
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14 pages, 4814 KB  
Article
Desorption of Ammonia Adsorbed on Prussian Blue Analogs by Washing with Saturated Ammonium Hydrogen Carbonate Solution
by Hatsuho Usuda, Yoshie Mishima, Tohru Kawamoto and Kimitaka Minami
Molecules 2022, 27(24), 8840; https://doi.org/10.3390/molecules27248840 - 13 Dec 2022
Cited by 10 | Viewed by 4304
Abstract
Prussian blue analogs (PBAs) have been reported as promising ammonia (NH3) adsorbents with a high capacity compared to activated carbon, zeolite, and ion exchange resins. The adsorbed NH3 was desorbed by heating and washing with water or acid. Recently, we [...] Read more.
Prussian blue analogs (PBAs) have been reported as promising ammonia (NH3) adsorbents with a high capacity compared to activated carbon, zeolite, and ion exchange resins. The adsorbed NH3 was desorbed by heating and washing with water or acid. Recently, we demonstrated that desorption was also possible by washing with a saturated ammonium hydrogen carbonate solution (sat. NH4HCO3aq) and recovered NH3 as an NH4HCO3 solid by introducing CO2 into the washing liquid after desorption. However, this has only been proven for copper ferrocyanide and the relationship between the adsorption/desorption behavior and metal ions in PBAs has not been identified. In this study, we investigated the adsorption/desorption behavior of PBAs that are complexes of first row transition metals with hexacyanometalate anions. Six types of PBAs were tested in this study and copper ferricyanide exhibited the highest desorption/adsorption ratio. X-ray diffraction results revealed high structural stability for cobalt hexacyanocobaltate (CoHCC) and nickel ferricyanide (NiHCF). The Fourier transform infrared spectroscopy results showed that the NH3 adsorbed on the vacancy sites tended to desorb compared to the NH3 adsorbed on the interstitial sites as ammonium ions. Interestingly, the desorption/adsorption ratio exhibited the Irving-Williams order. Full article
(This article belongs to the Special Issue Feature Papers in Materials Chemistry)
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27 pages, 5817 KB  
Article
The Effect of Combined Atmospheric Plasma/UV Treatments on Improving the Durability of Flame Retardants Applied to Cotton
by Maram Ayesh, Arthur Richard Horrocks and Baljinder K. Kandola
Molecules 2022, 27(24), 8737; https://doi.org/10.3390/molecules27248737 - 9 Dec 2022
Cited by 14 | Viewed by 2571
Abstract
Application of a combined atmospheric plasma/UV laser to cotton fabrics impregnated with selected non-durable flame retardants (FRs) has shown evidence of covalent grafting of the latter species on to cotton fibre surfaces. As a result, an increase in their durability to water-soaking for [...] Read more.
Application of a combined atmospheric plasma/UV laser to cotton fabrics impregnated with selected non-durable flame retardants (FRs) has shown evidence of covalent grafting of the latter species on to cotton fibre surfaces. As a result, an increase in their durability to water-soaking for 30 min at 40 °C has been recorded. Based on previous research plasma gases comprising Ar80%/CO220% or N280%/O220% were used to pre-expose cotton fabric prior to or after FR impregnation to promote the formation of radical species and increased –COOH groups on surface cellulosic chains, which would encourage formation of FR-cellulose bonds. Analysis by scanning electron microscopy (SEM/EDX), X-ray photoelectron spectroscopy (XPS) and thermal analysis (TGA) suggested that organophosphorus- and nitrogen- containing flame retarding species in the presence of the silicon-containing molecules such as 3-aminopropyltriethoxy silane (APTS) resulted in formation of FR-S-O-cellulose links, which gave rise to post-water-soaking FR retentions > 10%. Similarly, the organophosphorus FR, diethyl N, N bis (2-hydroxyethyl) aminomethylphosphonate (DBAP), after plasma/UV exposure produced similar percentage retention values possibly via (PO).O.cellulose bond formation, While none of the plasmas/UV-treated, FR-impregnated fabrics showed self-extinction behaviour, although burning rates reduced and significant char formation was evident, it has been shown that FR durability may be increased using plasma/UV treatments. Full article
(This article belongs to the Special Issue Flame-Resistant Materials)
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16 pages, 2368 KB  
Article
Direct Correlation of Surface Tension and Surface Composition of Ionic Liquid Mixtures—A Combined Vacuum Pendant Drop and Angle-Resolved X-ray Photoelectron Spectroscopy Study
by Ulrike Paap, Vera Seidl, Karsten Meyer, Florian Maier and Hans-Peter Steinrück
Molecules 2022, 27(23), 8561; https://doi.org/10.3390/molecules27238561 - 5 Dec 2022
Cited by 10 | Viewed by 2441
Abstract
We investigated the surface tension and surface composition of various mixtures of the two ionic liquids (ILs) 1-methyl-3-octyl-imidazolium hexafluorophosphate [C8C1Im][PF6] and 1,3-bis(polyethylene glycol)imidazolium iodide [(mPEG2)2Im]I in the temperature range from 230 [...] Read more.
We investigated the surface tension and surface composition of various mixtures of the two ionic liquids (ILs) 1-methyl-3-octyl-imidazolium hexafluorophosphate [C8C1Im][PF6] and 1,3-bis(polyethylene glycol)imidazolium iodide [(mPEG2)2Im]I in the temperature range from 230 to 370 K under ultraclean vacuum conditions. The surface tension was measured using a newly developed apparatus, and the surface composition was determined by angle-resolved X-ray photoelectron spectroscopy (ARXPS). In the pure ILs, the alkyl chains of [C8C1Im][PF6] and the PEG chains of [(mPEG2)2Im]I are enriched at the IL/vacuum interface. In the mixtures, a strong selective surface enrichment of the alkyl chains occurs, which is most pronounced at low [C8C1Im][PF6] contents. For the surface tension, strong deviations from an ideal mixing behaviour take place. By applying a simple approach based on the surface composition of the mixtures as deduced from ARXPS, we are able to predict and reproduce the experimentally measured temperature-dependent surface tension values with astonishingly high accuracy. Full article
(This article belongs to the Special Issue Properties and Applications of Ionic Liquids-Based Advanced Materials)
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17 pages, 2840 KB  
Article
The Chemistry of Phenylimidotechnetium(V) Complexes with Isocyanides: Steric and Electronic Factors
by Guilhem Claude, Laura Zeh, Maximilian Roca Jungfer, Adelheid Hagenbach, Joshua S. Figueroa and Ulrich Abram
Molecules 2022, 27(23), 8546; https://doi.org/10.3390/molecules27238546 - 4 Dec 2022
Cited by 7 | Viewed by 23811
Abstract
Organometallic approaches are of ongoing interest for the development of novel functional 99mTc radiopharmaceuticals, while the basic organotechnetium chemistry seems frequently to be little explored. Thus, structural and reactivity studies with the long-lived isotope 99Tc are of permanent interest as the [...] Read more.
Organometallic approaches are of ongoing interest for the development of novel functional 99mTc radiopharmaceuticals, while the basic organotechnetium chemistry seems frequently to be little explored. Thus, structural and reactivity studies with the long-lived isotope 99Tc are of permanent interest as the foundation for further progress in the related radiopharmaceutical research with this artificial element. Particularly the knowledge about the organometallic chemistry of high-valent technetium compounds is scarcely developed. Here, phenylimido complexes of technetium(V) with different isocyanides are introduced. They have been synthesized by ligand-exchange procedures starting from [Tc(NPh)Cl3(PPh3)2]. Different reactivity patterns and products have been obtained depending on the steric and electronic properties of the individual ligands. This involves the formation of 1:1 and 1:2 exchange products of Tc(V) with the general formulae [Tc(NPh)Cl3(PPh3)(isocyanide)], cis- or trans-[Tc(NPh)Cl3(isocyanide)2], but also the reduction in the metal and the formation of cationic technetium(I) complex of the formula [Tc(isocyanide)6]+ when p-fluorophenyl isocyanide is used. The products have been studied by single-crystal X-ray diffraction and spectroscopic methods, including IR and multinuclear NMR spectroscopy. DFT calculations on the different isocyanides allow the prediction of their reactivity towards electron-rich and electron-deficient metal centers by means of the empirical SADAP parameter, which has been derived from the potential energy surface of the electron density on their potentially coordinating carbon atoms. Full article
(This article belongs to the Special Issue Technetium and Rhenium in Chemistry and Their Advanced Applications)
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12 pages, 4011 KB  
Article
Toward High-Performance Electrochromic Conjugated Polymers: Influence of Local Chemical Environment and Side-Chain Engineering
by Kaiwen Lin, Changjun Wu, Guangyao Zhang, Zhixin Wu, Shiting Tang, Yingxin Lin, Xinye Li, Yuying Jiang, Hengjia Lin, Yuehui Wang, Shouli Ming and Baoyang Lu
Molecules 2022, 27(23), 8424; https://doi.org/10.3390/molecules27238424 - 1 Dec 2022
Cited by 17 | Viewed by 2610
Abstract
Three homologous electrochromic conjugated polymers, each containing an asymmetric building block but decorated with distinct alkyl chains, were designed and synthesized using electrochemical polymerization in this study. The corresponding monomers, namely T610FBTT810, DT6FBT, and DT48FBT, comprise the same backbone structure, i.e., an asymmetric [...] Read more.
Three homologous electrochromic conjugated polymers, each containing an asymmetric building block but decorated with distinct alkyl chains, were designed and synthesized using electrochemical polymerization in this study. The corresponding monomers, namely T610FBTT810, DT6FBT, and DT48FBT, comprise the same backbone structure, i.e., an asymmetric 5-fluorobenzo[c][1,2,5]thiadiazole unit substituted by two thiophene terminals, but were decorated with different types of alkyl chain (hexyl, 2-butyloctyl, 2-hexyldecyl, or 2-octyldecyl). The effects of the side-chain structure and asymmetric repeating unit on the optical absorption, electrochemistry, morphology, and electrochromic properties were investigated comparatively. It was found that the electrochromism conjugated polymer, originating from DT6FBT with the shortest and linear alkyl chain, exhibits the best electrochromic performance with a 25% optical contrast ratio and a 0.3 s response time. The flexible electrochromic device of PDT6FBT achieved reversible colors of navy and cyan between the neutral and oxidized states, consistent with the non-device phenomenon. These results demonstrate that subtle modification of the side chain is able to change the electrochromic properties of conjugated polymers. Full article
(This article belongs to the Special Issue Structure and Electronic Properties of Conjugated Polymers and Nanocomposites)
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24 pages, 2746 KB  
Review
Iridium and Ruthenium Complexes Bearing Perylene Ligands
by Luca Mauri, Alessia Colombo, Claudia Dragonetti, Francesco Fagnani and Dominique Roberto
Molecules 2022, 27(22), 7928; https://doi.org/10.3390/molecules27227928 - 16 Nov 2022
Cited by 4 | Viewed by 3326
Abstract
The present review summarizes the work carried out mostly in the last decade on iridium and ruthenium complexes bearing various perylene ligands, of particular interest for bioimaging, photodynamic therapy, and solar energy conversion. In these complexes, the absorption spectra and the electrochemical properties [...] Read more.
The present review summarizes the work carried out mostly in the last decade on iridium and ruthenium complexes bearing various perylene ligands, of particular interest for bioimaging, photodynamic therapy, and solar energy conversion. In these complexes, the absorption spectra and the electrochemical properties are those of the perylene subunit plus those of the metal moiety. In contrast, the emissions are completely changed with respect to perylenes considered alone. Thus, fully organic perylenes are characterized by a strong fluorescence in the visible region, lifetimes of a few nanoseconds, and luminescence quantum yields approaching 100%, whereas perylene Ir and Ru complexes usually do not emit; however, in few cases, weak phosphorescent emissions, with lifetimes in the range of microseconds and relatively low quantum yields, are reported. This is due to a strong interaction between the perylene core and the heavy metal center, taking place after the excitation. Nevertheless, an important advantage deriving from the presence of the heavy metal center is represented by the ability to generate large amounts of singlet oxygen, which plays a key role in photodynamic therapy. Full article
(This article belongs to the Special Issue Featured Reviews in Organometallic Chemistry)
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21 pages, 6322 KB  
Article
Selective Oxidation of Glycerol via Acceptorless Dehydrogenation Driven by Ir(I)-NHC Catalysts
by M. Victoria Jiménez, Ana I. Ojeda-Amador, Raquel Puerta-Oteo, Joaquín Martínez-Sal, Vincenzo Passarelli and Jesús J. Pérez-Torrente
Molecules 2022, 27(22), 7666; https://doi.org/10.3390/molecules27227666 - 8 Nov 2022
Cited by 8 | Viewed by 2883
Abstract
Iridium(I) compounds featuring bridge-functionalized bis-NHC ligands (NHC = N-heterocyclic carbene), [Ir(cod)(bis-NHC)] and [Ir(CO)2(bis-NHC)], have been prepared from the appropriate carboxylate- or hydroxy-functionalized bis-imidazolium salts. The related complexes [Ir(cod)(NHC)2]+ and [IrCl(cod)(NHC)(cod)] have been synthesized from a 3-hydroxypropyl functionalized imidazolium [...] Read more.
Iridium(I) compounds featuring bridge-functionalized bis-NHC ligands (NHC = N-heterocyclic carbene), [Ir(cod)(bis-NHC)] and [Ir(CO)2(bis-NHC)], have been prepared from the appropriate carboxylate- or hydroxy-functionalized bis-imidazolium salts. The related complexes [Ir(cod)(NHC)2]+ and [IrCl(cod)(NHC)(cod)] have been synthesized from a 3-hydroxypropyl functionalized imidazolium salt. These complexes have been shown to be robust catalysts in the oxidative dehydrogenation of glycerol to lactate (LA) with dihydrogen release. High activity and selectivity to LA were achieved in an open system under low catalyst loadings using KOH as a base. The hydroxy-functionalized bis-NHC catalysts are much more active than both the carboxylate-functionalized ones and the unbridged bis-NHC iridium(I) catalyst with hydroxyalkyl-functionalized NHC ligands. In general, carbonyl complexes are more active than the related 1,5-cyclooctadiene ones. The catalyst [Ir(CO)2{(MeImCH2)2CHOH}]Br exhibits the highest productivity affording TONs to LA up to 15,000 at very low catalyst loadings. Full article
(This article belongs to the Special Issue Synthesis, Characterization, and Catalytic Activity of Organometallic Complexes 2022)
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20 pages, 6561 KB  
Article
Molecular Engineering of Quinone-Based Nickel Complexes and Polymers for All-Organic Li-Ion Batteries
by Yanislav Danchovski, Hristo Rasheev, Radostina Stoyanova and Alia Tadjer
Molecules 2022, 27(20), 6805; https://doi.org/10.3390/molecules27206805 - 11 Oct 2022
Cited by 2 | Viewed by 2721
Abstract
All-organic Li-ion batteries appear to be a sustainable and safer alternative to the currently-used Li-ion batteries but their application is still limited due to the lack of organic compounds with high redox potentials toward Li+/Li0. Herein, we report a [...] Read more.
All-organic Li-ion batteries appear to be a sustainable and safer alternative to the currently-used Li-ion batteries but their application is still limited due to the lack of organic compounds with high redox potentials toward Li+/Li0. Herein, we report a computational design of nickel complexes and coordination polymers that have redox potentials spanning the full voltage range: from the highest, 4.7 V, to the lowest, 0.4 V. The complexes and polymers are modeled by binding low- and high-oxidized Ni ions (i.e., Ni(II) and Ni(IV)) to redox-active para-benzoquinone molecules substituted with carboxyl- and cyano-groups. It is found that both the nickel ions and the quinone-derived ligands are redox-active upon lithiation. The type of Ni coordination also has a bearing on the redox potentials. By combining the complex of Ni(IV) with 2-carboxylato-5-cyano-1,4-benzoquinones as a cathode and Ni(II)-2,5-dicarboxylato-3,6-dicyano-1,4-benzoquinone coordination polymer as an anode, all-organic Li-ion batteries could be assembled, operating at an average voltage exceeding 3.0 V and delivering a capacity of more than 300 mAh/g. Full article
(This article belongs to the Special Issue Metal-Organic Complexes: Applications in Chemistry and Materials Science)
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29 pages, 9817 KB  
Article
A Journey through Diastereomeric Space: The Design, Synthesis, In Vitro and In Vivo Pharmacological Activity, and Molecular Modeling of Novel Potent Diastereomeric MOR Agonists and Antagonists
by Dana R. Chambers, Agnieszka Sulima, Dan Luo, Thomas E. Prisinzano, Alexander Goldberg, Bing Xie, Lei Shi, Carol A. Paronis, Jack Bergman, Nima Nassehi, Dana E. Selley, Gregory H. Imler, Arthur E. Jacobson and Kenner C. Rice
Molecules 2022, 27(19), 6455; https://doi.org/10.3390/molecules27196455 - 30 Sep 2022
Cited by 9 | Viewed by 3113
Abstract
Four sets of diastereomeric C9-alkenyl 5-phenylmorphans, varying in the length of the C9-alkenyl chain, were designed to examine the effect of these spatially distinct ligands on opioid receptors. Functional activity was obtained by forskolin-induced cAMP accumulation assays and several compounds were examined in [...] Read more.
Four sets of diastereomeric C9-alkenyl 5-phenylmorphans, varying in the length of the C9-alkenyl chain, were designed to examine the effect of these spatially distinct ligands on opioid receptors. Functional activity was obtained by forskolin-induced cAMP accumulation assays and several compounds were examined in the [35S]GTPgS assay and in an assay for respiratory depression. In each of the four sets, similarities and differences were observed dependent on the length of their C9-alkenyl chain and, most importantly, their stereochemistry. Three MOR antagonists were found to be as or more potent than naltrexone and, unlike naltrexone, none had MOR, KOR, or DOR agonist activity. Several potent MOR full agonists were obtained, and, of particular interest partial agonists were found that exhibited less respiratory depression than that caused by morphine. The effect of stereochemistry and the length of the C9-alkenyl chain was also explored using molecular modeling. The MOR antagonists were found to interact with the inactive (4DKL) MOR crystal structures and agonists were found to interact with the active (6DDF) MOR crystal structures. The comparison of their binding modes at the mouse MOR was used to gain insight into the structural basis for their stereochemically induced pharmacological differences. Full article
(This article belongs to the Section Medicinal Chemistry)
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19 pages, 7069 KB  
Article
Detailed Structural Characterization of Oxidized Sucrose and Its Application in the Fully Carbohydrate-Based Preparation of a Hydrogel from Carboxymethyl Chitosan
by Hiroyuki Kono, Junki Noda and Haruki Wakamori
Molecules 2022, 27(18), 6137; https://doi.org/10.3390/molecules27186137 - 19 Sep 2022
Cited by 8 | Viewed by 3960
Abstract
Oxidized sucrose (OS) is a bio-based cross-linking agent with excellent biological safety and environmental non-toxicity. However, the precise structure of OS has not been elucidated owing to its structural complexity and low purity. Accordingly, in this study, complete chemical shift assignments were performed [...] Read more.
Oxidized sucrose (OS) is a bio-based cross-linking agent with excellent biological safety and environmental non-toxicity. However, the precise structure of OS has not been elucidated owing to its structural complexity and low purity. Accordingly, in this study, complete chemical shift assignments were performed by applying various nuclear magnetic resonance techniques, which permitted the structural and quantitative characterization of the two main OS products, each of which contained four aldehyde groups. In addition, we investigated the use of OS as a cross-linking agent in the preparation of a hydrogel from carboxymethyl chitosan (CMC), one of the most popular polysaccharides for use in biomedical applications. The primary amine groups of CMC were immediately cross-linked with the aldehyde groups of OS to form hydrogels without the requirement for a catalyst. It was found that the degree of cross-linking could be easily controlled by the feed amount of OS during CMC hydrogel preparation and the final cross-linking degree affected the thermal, swelling, and rheological properties of the obtained hydrogel. The results presented in this study are therefore expected to be applicable in the preparation of fully carbohydrate-based hydrogels for medical and pharmaceutical applications. Full article
(This article belongs to the Section Macromolecular Chemistry)
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31 pages, 8073 KB  
Review
Guanidinates as Alternative Ligands for Organometallic Complexes
by Fernando Carrillo-Hermosilla, Rafael Fernández-Galán, Alberto Ramos and David Elorriaga
Molecules 2022, 27(18), 5962; https://doi.org/10.3390/molecules27185962 - 13 Sep 2022
Cited by 22 | Viewed by 5175
Abstract
For decades, ligands such as phosphanes or cyclopentadienyl ring derivatives have dominated Coordination and Organometallic Chemistry. At the same time, alternative compounds have emerged that could compete either for a more practical and accessible synthesis or for greater control of steric and electronic [...] Read more.
For decades, ligands such as phosphanes or cyclopentadienyl ring derivatives have dominated Coordination and Organometallic Chemistry. At the same time, alternative compounds have emerged that could compete either for a more practical and accessible synthesis or for greater control of steric and electronic properties. Guanidines, nitrogen-rich compounds, appear as one such potential alternatives as ligands or proligands. In addition to occurring in a plethora of natural compounds, and thus in compounds of pharmacological use, guanidines allow a wide variety of coordination modes to different metal centers along the periodic table, with their monoanionic chelate derivatives being the most common. In this review, we focused on the organometallic chemistry of guanidinato compounds, discussing selected examples of coordination modes, reactivity and uses in catalysis or materials science. We believe that these amazing ligands offer a new promise in Organometallic Chemistry. Full article
(This article belongs to the Special Issue Organometallic Complexes: Fundamentals and Applications)
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11 pages, 2175 KB  
Article
Customizing Pore System in a Microporous Metal–Organic Framework for Efficient C2H2 Separation from CO2 and C2H4
by Qiang Zhang, Guan-Nan Han, Xin Lian, Shan-Qing Yang and Tong-Liang Hu
Molecules 2022, 27(18), 5929; https://doi.org/10.3390/molecules27185929 - 12 Sep 2022
Cited by 9 | Viewed by 5226
Abstract
Selective-adsorption separation is an energy-efficient technology for the capture of acetylene (C2H2) from carbon dioxide (CO2) and ethylene (C2H4). However, it remains a critical challenge to effectively recognize C2H2 among [...] Read more.
Selective-adsorption separation is an energy-efficient technology for the capture of acetylene (C2H2) from carbon dioxide (CO2) and ethylene (C2H4). However, it remains a critical challenge to effectively recognize C2H2 among CO2 and C2H4, owing to their analogous molecule sizes and physical properties. Herein, we report a new microporous metal–organic framework (NUM-14) possessing a carefully tailored pore system containing moderate pore size and nitro-functionalized channel surface for efficient separation of C2H2 from CO2 and C2H4. The activated NUM-14 (namely NUM-14a) exhibits sufficient pore space to acquire excellent C2H2 loading capacity (4.44 mmol g−1) under ambient conditions. In addition, it possesses dense nitro groups, acting as hydrogen bond acceptors, to selectively identify C2H2 molecules rather than CO2 and C2H4. The breakthrough experiments demonstrate the good actual separation ability of NUM-14a for C2H2/CO2 and C2H2/C2H4 mixtures. Furthermore, Grand Canonical Monte Carlo simulations indicate that the pore surface of the NUM-14a has a stronger affinity to preferentially bind C2H2 over CO2 and C2H4 via stronger C-H···O hydrogen bond interactions. This article provides some insights into customizing pore systems with desirable pore sizes and modifying groups in terms of MOF materials toward the capture of C2H2 from CO2 and C2H4 to promote the development of more MOF materials with excellent properties for gas adsorption and separation. Full article
(This article belongs to the Special Issue Advanced Crystalline Porous Material and Engineering for Separation and Catalysis Application)
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30 pages, 11934 KB  
Review
Azobenzene as Antimicrobial Molecules
by Miriam Di Martino, Lucia Sessa, Martina Di Matteo, Barbara Panunzi, Stefano Piotto and Simona Concilio
Molecules 2022, 27(17), 5643; https://doi.org/10.3390/molecules27175643 - 1 Sep 2022
Cited by 44 | Viewed by 7622
Abstract
Azo molecules, characterized by the presence of a -N=N- double bond, are widely used in various fields due to their sensitivity to external stimuli, ch as light. The emergence of bacterial resistance has pushed research towards designing new antimicrobial molecules that are more [...] Read more.
Azo molecules, characterized by the presence of a -N=N- double bond, are widely used in various fields due to their sensitivity to external stimuli, ch as light. The emergence of bacterial resistance has pushed research towards designing new antimicrobial molecules that are more efficient than those currently in use. Many authors have attempted to exploit the antimicrobial activity of azobenzene and to utilize their photoisomerization for selective control of the bioactivities of antimicrobial molecules, which is necessary for antibacterial therapy. This review will provide a systematic and consequential approach to coupling azobenzene moiety with active antimicrobial molecules and drugs, including small and large organic molecules, such as peptides. A selection of significant cutting-edge articles collected in recent years has been discussed, based on the structural pattern and antimicrobial performance, focusing especially on the photoactivity of azobenzene and the design of smart materials as the most targeted and desirable application. Full article
(This article belongs to the Special Issue Recent Advances in Antimicrobial Materials)
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19 pages, 2083 KB  
Review
Rhenium Radioisotopes for Medicine, a Focus on Production and Applications
by Licia Uccelli, Petra Martini, Luca Urso, Teresa Ghirardi, Lorenza Marvelli, Corrado Cittanti, Aldo Carnevale, Melchiore Giganti, Mirco Bartolomei and Alessandra Boschi
Molecules 2022, 27(16), 5283; https://doi.org/10.3390/molecules27165283 - 18 Aug 2022
Cited by 25 | Viewed by 5700
Abstract
In recent decades, the use of alpha; pure beta; or beta/gamma emitters in oncology, endocrinology, and interventional cardiology rheumatology, has proved to be an important alternative to the most common therapeutic regimens. Among radionuclides used for therapy in nuclear medicine, two rhenium radioisotopes [...] Read more.
In recent decades, the use of alpha; pure beta; or beta/gamma emitters in oncology, endocrinology, and interventional cardiology rheumatology, has proved to be an important alternative to the most common therapeutic regimens. Among radionuclides used for therapy in nuclear medicine, two rhenium radioisotopes are of particular relevance: rhenium-186 and rhenium-188. The first is routinely produced in nuclear reactors by direct neutron activation of rhenium-186 via 185Re(n,γ)186Re nuclear reaction. Rhenium-188 is produced by the decay of the parent tungsten-188. Separation of rhenium-188 is mainly performed using a chromatographic 188W/188Re generator in which tungsten-188 is adsorbed on the alumina column, similar to the 99Mo/99mTc generator system, and the radionuclide eluted in saline solution. The application of rhenium-186 and rhenium-188 depends on their specific activity. Rhenium-186 is produced in low specific activity and is mainly used for labeling particles or diphosphonates for bone pain palliation. Whereas, rhenium-188 of high specific activity can be used for labeling peptides or bioactive molecules. One of the advantages of rhenium is its chemical similarity with technetium. So, diagnostic technetium analogs labeled with radiorhenium can be developed for therapeutic applications. Clinical trials promoting the use of 186/188Re-radiopharmaceuticals is, in particular, are discussed. Full article
(This article belongs to the Special Issue Exclusive Contributions by the Editorial Board Members (EBMs) of the Inorganic Chemistry Section of Molecules)
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20 pages, 2079 KB  
Article
Design, Synthesis and Preliminary Evaluation of the Cytotoxicity and Antibacterial Activity of Novel Triphenylphosphonium Derivatives of Betulin
by Mirosława Grymel, Anna Lalik, Alicja Kazek-Kęsik, Marietta Szewczyk, Patrycja Grabiec and Karol Erfurt
Molecules 2022, 27(16), 5156; https://doi.org/10.3390/molecules27165156 - 12 Aug 2022
Cited by 20 | Viewed by 2923
Abstract
For several decades, natural products have been widely researched and their native scaffolds are the basis for the design and synthesis of new potential therapeutic agents. Betulin is an interesting biologically attractive natural parent molecule with a high safety profile and can easily [...] Read more.
For several decades, natural products have been widely researched and their native scaffolds are the basis for the design and synthesis of new potential therapeutic agents. Betulin is an interesting biologically attractive natural parent molecule with a high safety profile and can easily undergo a variety of structural modifications. Herein, we describe the synthesis of new molecular hybrids of betulin via covalent linkage with an alkyltriphenylphosphonium moiety. The proposed strategy enables the preparation of semi-synthetic derivatives (28-TPP⊕ BN and 3,28-bisTPP⊕ BN) from betulin through simple transformations in high yields. The obtained results showed that the presence of a lipophilic cation improved the solubility of the tested analogs compared to betulin, and increased their cytotoxicity. Among the triphenylphosphonium derivatives tested, analogs 7a (IC50 of 5.56 µM) and 7b (IC50 of 5.77 µM) demonstrated the highest cytotoxicity against the colorectal carcinoma cell line (HCT 116). TPP⊕-conjugates with betulin showed antimicrobial properties against Gram-positive reference Staphylococcus aureus ATCC 25923 and Staphylococcus epidermidis ATCC 12228 bacteria, at a 200 µM concentration in water. Hence, the conjugation of betulin’s parent backbone with a triphenylphosphonium moiety promotes transport through the hydrophobic barriers of the mitochondrial membrane, making it a promising strategy to improve the bioavailability of natural substances. Full article
(This article belongs to the Special Issue Organophosphorus Chemistry: A New Perspective)
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31 pages, 9627 KB  
Review
Bidentate Donor-Functionalized N-Heterocyclic Carbenes: Valuable Ligands for Ruthenium-Catalyzed Transfer Hydrogenation
by Vincent Ritleng and Christophe Michon
Molecules 2022, 27(15), 4703; https://doi.org/10.3390/molecules27154703 - 23 Jul 2022
Cited by 11 | Viewed by 2994
Abstract
Ruthenium complexes are by far the most studied compounds that catalyze hydrogen transfer reactions. In this review, we describe the use in this field of ruthenium complexes bearing bidentate donor-functionalized N-heterocyclic carbene ligands. The review specifically covers the application in transfer hydrogenations [...] Read more.
Ruthenium complexes are by far the most studied compounds that catalyze hydrogen transfer reactions. In this review, we describe the use in this field of ruthenium complexes bearing bidentate donor-functionalized N-heterocyclic carbene ligands. The review specifically covers the application in transfer hydrogenations of (κ2-CNHC,Y)-ruthenacyclic compounds where the Y donor atom is a N, P, O, or S atom, and where the N-heterocyclic carbene ligand is a classical imidazol-2-ylidene, a benzimidazol-2-ylidene, a mesoionic 1,2,3-triazolylidene, or an imidazol-4-ylidene ligand. Tridentate donor-functionalized N-heterocyclic carbene complexes thus fall outside the scope of the review. Applications in (asymmetric) transfer hydrogenation of ketones, aldehydes, imines, alkenes, and nitrobenzene are discussed. Full article
(This article belongs to the Special Issue Featured Reviews in Organometallic Chemistry)
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17 pages, 14047 KB  
Review
Recent Advances in Self-Assembly and Application of Para-Aramids
by Chunjie Xie, Shixuan Yang, Ran He, Jianning Liu, Yuexi Chen, Yongyi Guo, Zhaoxia Guo, Teng Qiu and Xinlin Tuo
Molecules 2022, 27(14), 4413; https://doi.org/10.3390/molecules27144413 - 9 Jul 2022
Cited by 18 | Viewed by 5058
Abstract
Poly(p-phenylene terephthalamide) (PPTA) is one kind of lyotropic liquid crystal polymer. Kevlar fibers performed from PPTA are widely used in many fields due to their superior mechanical properties resulting from their highly oriented macromolecular structure. However, the “infusible and insoluble” characteristic [...] Read more.
Poly(p-phenylene terephthalamide) (PPTA) is one kind of lyotropic liquid crystal polymer. Kevlar fibers performed from PPTA are widely used in many fields due to their superior mechanical properties resulting from their highly oriented macromolecular structure. However, the “infusible and insoluble” characteristic of PPTA gives rise to its poor processability, which limits its scope of application. The strong interactions and orientation characteristic of aromatic amide segments make PPTA attractive in the field of self-assembly. Chemical derivation has proved an effective way to modify the molecular structure of PPTA to improve its solubility and amphiphilicity, which resulted in different liquid crystal behaviors or supramolecular aggregates, but the modification of PPTA is usually complex and difficult. Alternatively, higher-order all-PPTA structures have also been realized through the controllable hierarchical self-assembly of PPTA from the polymerization process to the formation of macroscopic products. This review briefly summarizes the self-assembly methods of PPTA-based materials in recent years, and focuses on the polymerization-induced PPTA nanofibers which can be further fabricated into different macroscopic architectures when other self-assembly methods are combined. This monomer-started hierarchical self-assembly strategy evokes the feasible processing of PPTA, and enriches the diversity of product, which is expected to be expanded to other liquid crystal polymers. Full article
(This article belongs to the Special Issue Hierarchical Assembly and Micro-/Nano-Structured Liquid Crystal Soft Materials toward Novel Applications beyond Display)
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38 pages, 4530 KB  
Review
Microwave-Assisted Synthesis: Can Transition Metal Complexes Take Advantage of This “Green” Method?
by Elisabetta Gabano and Mauro Ravera
Molecules 2022, 27(13), 4249; https://doi.org/10.3390/molecules27134249 - 30 Jun 2022
Cited by 42 | Viewed by 13383
Abstract
Microwave-assisted synthesis is considered environmental-friendly and, therefore, in agreement with the principles of green chemistry. This form of energy has been employed extensively and successfully in organic synthesis also in the case of metal-catalyzed synthetic procedures. However, it has been less widely exploited [...] Read more.
Microwave-assisted synthesis is considered environmental-friendly and, therefore, in agreement with the principles of green chemistry. This form of energy has been employed extensively and successfully in organic synthesis also in the case of metal-catalyzed synthetic procedures. However, it has been less widely exploited in the synthesis of metal complexes. As microwave irradiation has been proving its utility as both a time-saving procedure and an alternative way to carry on tricky transformations, its use can help inorganic chemists, too. This review focuses on the use of microwave irradiation in the preparation of transition metal complexes and organometallic compounds and also includes new, unpublished results. The syntheses of the compounds are described following the group of the periodic table to which the contained metal belongs. A general overview of the results from over 150 papers points out that microwaves can be a useful synthetic tool for inorganic chemists, reducing dramatically the reaction times with respect to traditional heating. This is often accompanied by a more limited risk of decomposition of reagents or products by an increase in yield, purity, and (sometimes) selectivity. In any case, thermal control is operative, whereas nonthermal or specific microwave effects seem to be absent. Full article
(This article belongs to the Special Issue Exclusive Contributions by the Editorial Board Members (EBMs) of the Inorganic Chemistry Section of Molecules)
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23 pages, 6089 KB  
Review
Poly(Lactic Acid)-Based Graft Copolymers: Syntheses Strategies and Improvement of Properties for Biomedical and Environmentally Friendly Applications: A Review
by Jean Coudane, Hélène Van Den Berghe, Julia Mouton, Xavier Garric and Benjamin Nottelet
Molecules 2022, 27(13), 4135; https://doi.org/10.3390/molecules27134135 - 28 Jun 2022
Cited by 34 | Viewed by 7650
Abstract
As a potential replacement for petroleum-based plastics, biodegradable bio-based polymers such as poly(lactic acid) (PLA) have received much attention in recent years. PLA is a biodegradable polymer with major applications in packaging and medicine. Unfortunately, PLA is less flexible and has less impact [...] Read more.
As a potential replacement for petroleum-based plastics, biodegradable bio-based polymers such as poly(lactic acid) (PLA) have received much attention in recent years. PLA is a biodegradable polymer with major applications in packaging and medicine. Unfortunately, PLA is less flexible and has less impact resistance than petroleum-based plastics. To improve the mechanical properties of PLA, PLA-based blends are very often used, but the outcome does not meet expectations because of the non-compatibility of the polymer blends. From a chemical point of view, the use of graft copolymers as a compatibilizer with a PLA backbone bearing side chains is an interesting option for improving the compatibility of these blends, which remains challenging. This review article reports on the various graft copolymers based on a PLA backbone and their syntheses following two chemical strategies: the synthesis and polymerization of modified lactide or direct chemical post-polymerization modification of PLA. The main applications of these PLA graft copolymers in the environmental and biomedical fields are presented. Full article
(This article belongs to the Special Issue Polylactide-Based Materials: Synthesis and Biomedical Applications)
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22 pages, 5227 KB  
Article
Supramolecular cis-“Bis(Chelation)” of [M(CN)6]3− (M = CrIII, FeIII, CoIII) by Phloroglucinol (H3PG)
by Katarzyna Jędrzejowska, Jedrzej Kobylarczyk, Dorota Glosz, Emilia Kuzniak-Glanowska, Dominika Tabor, Monika Srebro-Hooper, Jakub J. Zakrzewski, Katarzyna Dziedzic-Kocurek, Tadeusz M. Muzioł and Robert Podgajny
Molecules 2022, 27(13), 4111; https://doi.org/10.3390/molecules27134111 - 26 Jun 2022
Cited by 3 | Viewed by 5540
Abstract
Studies on molecular co-crystal type materials are important in the design and preparation of easy-to-absorb drugs, non-centrosymmetric, and chiral crystals for optical performance, liquid crystals, or plastic phases. From a fundamental point of view, such studies also provide useful information on various supramolecular [...] Read more.
Studies on molecular co-crystal type materials are important in the design and preparation of easy-to-absorb drugs, non-centrosymmetric, and chiral crystals for optical performance, liquid crystals, or plastic phases. From a fundamental point of view, such studies also provide useful information on various supramolecular synthons and molecular ordering, including metric parameters, molecular matching, energetical hierarchy, and combinatorial potential, appealing to the rational design of functional materials through structure–properties–application schemes. Co-crystal salts involving anionic d-metallate coordination complexes are moderately explored (compared to the generality of co-crystals), and in this context, we present a new series of isomorphous co-crystalline salts (PPh4)3[M(CN)6](H3PG)2·2MeCN (M = Cr, 1; Fe, 2; Co 3; H3PG = phloroglucinol, 1,3,5-trihydroxobenzene). In this study, 1–3 were characterized experimentally using SC XRD, Hirshfeld analysis, ESI-MS spectrometry, vibrational IR and Raman, 57Fe Mössbauer, electronic absorption UV-Vis-NIR, and photoluminescence spectroscopies, and theoretically with density functional theory calculations. The two-dimensional square grid-like hydrogen-bond {[M(CN)6]3−;(H3PG)2}∞ network features original {[M(CN)6]3−;(H3PG)4} supramolecular cis-bis(chelate) motifs involving: (i) two double cyclic hydrogen bond synthons M(-CN⋅⋅⋅HO-)2Ar, {[M(CN)6]3−;H2PGH}, between cis-oriented cyanido ligands of [M(CN)6]3− and resorcinol-like face of H3PG, and (ii) two single hydrogen bonds M-CN⋅⋅⋅HO-Ar, {[M(CN)6]3−;HPGH2}, involving the remaining two cyanide ligands. The occurrence of the above tectonic motif is discussed with regard to the relevant data existing in the CCDC database, including the multisite H-bond binding of [M(CN)6]3− by organic species, mononuclear coordination complexes, and polynuclear complexes. The physicochemical and computational characterization discloses notable spectral modifications under the regime of an extended hydrogen bond network. Full article
(This article belongs to the Special Issue Exclusive Contributions by the Editorial Board Members (EBMs) of the Inorganic Chemistry Section of Molecules)
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16 pages, 3389 KB  
Article
Characterization of CM-398, a Novel Selective Sigma-2 Receptor Ligand, as a Potential Therapeutic for Neuropathic Pain
by Lisa L. Wilson, Amy R. Alleyne, Shainnel O. Eans, Thomas J. Cirino, Heather M. Stacy, Marco Mottinelli, Sebastiano Intagliata, Christopher R. McCurdy and Jay P. McLaughlin
Molecules 2022, 27(11), 3617; https://doi.org/10.3390/molecules27113617 - 4 Jun 2022
Cited by 19 | Viewed by 4097
Abstract
Sigma receptors modulate nociception, offering a potential therapeutic target to treat pain, but relatively little is known regarding the role of sigma-2 receptors (S2R) in nociception. The purpose of this study was to investigate the in vivo analgesic and anti-allodynic activity and liabilities [...] Read more.
Sigma receptors modulate nociception, offering a potential therapeutic target to treat pain, but relatively little is known regarding the role of sigma-2 receptors (S2R) in nociception. The purpose of this study was to investigate the in vivo analgesic and anti-allodynic activity and liabilities of a novel S2R selective ligand, 1-[4-(6,7-dimethoxy-1,2,3,4-tetrahydroisoquinolin-2-yl)butyl]-3-methyl-1,3-dihydro-1,3-benzimidazol-2-one (CM-398). The inhibition of thermal, induced chemical, or inflammatory pain as well as the allodynia resulting from chronic nerve constriction injury (CCI) model of neuropathic pain were assessed in male mice. CM-398 dose-dependently (10–45 mg/kg i.p.) reduced mechanical allodynia in the CCI neuropathic pain model, equivalent at the higher dose to the effect of the control analgesic gabapentin (50 mg/kg i.p.). Likewise, pretreatment (i.p.) with CM-398 dose-dependently produced antinociception in the acetic acid writhing test (ED50 (and 95% C.I.) = 14.7 (10.6–20) mg/kg, i.p.) and the formalin assay (ED50 (and 95% C.I.) = 0.86 (0.44–1.81) mg/kg, i.p.) but was without effect in the 55 °C warm-water tail-withdrawal assay. A high dose of CM-398 (45 mg/kg, i.p.) exhibited modest locomotor impairment in a rotarod assay and conditioned place aversion, potentially complicating the interpretation of nociceptive testing. However, in an operant pain model resistant to these confounds, mice experiencing CCI and treated with CM-398 demonstrated robust conditioned place preference. Overall, these results demonstrate the S2R selective antagonist CM-398 produces antinociception and anti-allodynia with fewer liabilities than established therapeutics, adding to emerging data suggesting possible mediation of nociception by S2R, and the development of S2R ligands as potential treatments for chronic pain. Full article
(This article belongs to the Special Issue Featured Papers in Medicinal Chemistry)
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15 pages, 3240 KB  
Article
Synthesis, Crystal Structure and Magnetic Properties of a Trinuclear Copper(II) Complex Based on P-Cresol-Substituted Bis(α-Nitronyl Nitroxide) Biradical
by Sabrina Grenda, Maxime Beau and Dominique Luneau
Molecules 2022, 27(10), 3218; https://doi.org/10.3390/molecules27103218 - 18 May 2022
Cited by 6 | Viewed by 3483
Abstract
Trinuclear copper(II) complex [CuII3(NIT2PhO)2Cl4] was synthesized with p-cresol-substituted bis(α-nitronyl nitroxide) biradical: 4-methyl-2,6-bis(1-oxyl-3-oxido-4,4,5,5-tetramethyl-2-imidazolin-2-yl)phenol (NIT2PhOH). The crystal structure of this heterospin complex was determined using single-crystal X-ray diffraction analysis and exhibits four unusual seven-membered [...] Read more.
Trinuclear copper(II) complex [CuII3(NIT2PhO)2Cl4] was synthesized with p-cresol-substituted bis(α-nitronyl nitroxide) biradical: 4-methyl-2,6-bis(1-oxyl-3-oxido-4,4,5,5-tetramethyl-2-imidazolin-2-yl)phenol (NIT2PhOH). The crystal structure of this heterospin complex was determined using single-crystal X-ray diffraction analysis and exhibits four unusual seven-membered metallocycles formed from the coordination of oxygen atoms of the N-O groups and of bridging phenoxo (µ-PhO−) moieties with copper(II) ions. The crystal structure analysis reveals an incipient agostic interaction between a square planar copper center and a hydrogen-carbon bond from one methyl group carried on the coordinated nitronyl-nitroxide radical. The intramolecular Cu∙∙∙H-C interaction involves a six-membered metallocycle and may stabilize the copper center in square planar coordination mode. From the magnetic susceptibility measurements, the complex, which totals seven S = 1/2 spin carriers, has almost a ground state spin S = 1/2 at room temperature ascribed to strong antiferromagnetic interaction between the nitronyl nitroxide moieties and the copper(II) centers and in between the copper(II) centers through the bridging phenoxo oxygen atom. Full article
(This article belongs to the Special Issue Crystal Structures of Metal Complexes)
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13 pages, 2073 KB  
Article
Conditions to Control Furan Ring Opening during Furfuryl Alcohol Polymerization
by Lucie Quinquet, Pierre Delliere and Nathanael Guigo
Molecules 2022, 27(10), 3212; https://doi.org/10.3390/molecules27103212 - 17 May 2022
Cited by 14 | Viewed by 4936
Abstract
The chemistry of biomass-derived furans is particularly sensitive to ring openings. These side reactions occur during furfuryl alcohol polymerization. In this work, the furan ring-opening was controlled by changing polymerization conditions, such as varying the type of acidic initiator or the water content. [...] Read more.
The chemistry of biomass-derived furans is particularly sensitive to ring openings. These side reactions occur during furfuryl alcohol polymerization. In this work, the furan ring-opening was controlled by changing polymerization conditions, such as varying the type of acidic initiator or the water content. The degree of open structures (DOS) was determined by quantifying the formed carbonyl species by means of quantitative 19F NMR and potentiometric titration. The progress of polymerization and ring opening were monitored by DSC and FT-IR spectroscopy. The presence of additional water is more determining on ring opening than the nature of the acidic initiator. Qualitative structural assessment by means of 13C NMR and FT-IR shows that, depending on the employed conditions, poly(furfuryl alcohol) samples can be classified in two groups. Indeed, either more ester or more ketone side groups are formed as a result of side ring opening reactions. The absence of additional water during FA polymerization preferentially leads to opened structures in the PFA bearing more ester moieties. Full article
(This article belongs to the Special Issue Natural Polymers and Biopolymers III)
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26 pages, 6258 KB  
Article
Affinity Proteomics Identifies Interaction Partners and Defines Novel Insights into the Function of the Adhesion GPCR VLGR1/ADGRV1
by Barbara Knapp, Jens Roedig, Heiko Roedig, Jacek Krzysko, Nicola Horn, Baran E. Güler, Deva Krupakar Kusuluri, Adem Yildirim, Karsten Boldt, Marius Ueffing, Ines Liebscher and Uwe Wolfrum
Molecules 2022, 27(10), 3108; https://doi.org/10.3390/molecules27103108 - 12 May 2022
Cited by 15 | Viewed by 5312
Abstract
The very large G-protein-coupled receptor 1 (VLGR1/ADGRV1) is the largest member of the adhesion G-protein-coupled receptor (ADGR) family. Mutations in VLGR1/ADGRV1 cause human Usher syndrome (USH), a form of hereditary deaf-blindness, and have been additionally linked to epilepsy. In the absence of tangible [...] Read more.
The very large G-protein-coupled receptor 1 (VLGR1/ADGRV1) is the largest member of the adhesion G-protein-coupled receptor (ADGR) family. Mutations in VLGR1/ADGRV1 cause human Usher syndrome (USH), a form of hereditary deaf-blindness, and have been additionally linked to epilepsy. In the absence of tangible knowledge of the molecular function and signaling of VLGR1, the pathomechanisms underlying the development of these diseases are still unknown. Our study aimed to identify novel, previously unknown protein networks associated with VLGR1 in order to describe new functional cellular modules of this receptor. Using affinity proteomics, we have identified numerous new potential binding partners and ligands of VLGR1. Tandem affinity purification hits were functionally grouped based on their Gene Ontology terms and associated with functional cellular modules indicative of functions of VLGR1 in transcriptional regulation, splicing, cell cycle regulation, ciliogenesis, cell adhesion, neuronal development, and retinal maintenance. In addition, we validated the identified protein interactions and pathways in vitro and in situ. Our data provided new insights into possible functions of VLGR1, related to the development of USH and epilepsy, and also suggest a possible role in the development of other neuronal diseases such as Alzheimer’s disease. Full article
(This article belongs to the Special Issue Molecular Modeling, Synthesis, and Functional Characterization of GPCR (G-Protein Coupled Receptor) Ligands)
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25 pages, 13682 KB  
Review
Synthesis and Applications of Nitrogen-Containing Heterocycles as Antiviral Agents
by Tuyen N. Tran and Maged Henary
Molecules 2022, 27(9), 2700; https://doi.org/10.3390/molecules27092700 - 22 Apr 2022
Cited by 66 | Viewed by 8042
Abstract
Viruses have been a long-term source of infectious diseases that can lead to large-scale infections and massive deaths. Especially with the recent highly contagious coronavirus (COVID-19), antiviral drugs were developed nonstop to deal with the emergence of new viruses and subject to drug [...] Read more.
Viruses have been a long-term source of infectious diseases that can lead to large-scale infections and massive deaths. Especially with the recent highly contagious coronavirus (COVID-19), antiviral drugs were developed nonstop to deal with the emergence of new viruses and subject to drug resistance. Nitrogen-containing heterocycles have compatible structures and properties with exceptional biological activity for the drug design of antiviral agents. They provided a broad spectrum of interference against viral infection at various stages, from blocking early viral entry to disrupting the viral genome replication process by targeting different enzymes and proteins of viruses. This review focused on the synthesis and application of antiviral agents derived from various nitrogen-containing heterocycles, such as indole, pyrrole, pyrimidine, pyrazole, and quinoline, within the last ten years. The synthesized scaffolds target HIV, HCV/HBV, VZV/HSV, SARS-CoV, COVID-19, and influenza viruses. Full article
(This article belongs to the Special Issue Synthesis of Heteroaromatic Compounds)
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23 pages, 393 KB  
Review
The Use of Cerium Compounds as Antimicrobials for Biomedical Applications
by Emilia Barker, Joanna Shepherd and Ilida Ortega Asencio
Molecules 2022, 27(9), 2678; https://doi.org/10.3390/molecules27092678 - 21 Apr 2022
Cited by 75 | Viewed by 6022
Abstract
Cerium and its derivatives have been used as remedies for wounds since the early 20th century. Cerium nitrate has attracted most attention in the treatment of deep burns, followed later by reports of its antimicrobial properties. Its ability to mimic and replace calcium [...] Read more.
Cerium and its derivatives have been used as remedies for wounds since the early 20th century. Cerium nitrate has attracted most attention in the treatment of deep burns, followed later by reports of its antimicrobial properties. Its ability to mimic and replace calcium is presumed to be a major mechanism of its beneficial action. However, despite some encouraging results, the overall data are somewhat confusing with seemingly the same compounds yielding opposing results. Despite this, cerium nitrate is currently used in wound treatment in combination with silver sulfadiazine as Flammacérium. Cerium oxide, especially in nanoparticle form (Nanoceria), has lately captured much interest due to its antibacterial properties mediated via oxidative stress, leading to an increase of published reports. The properties of Nanoceria depend on the synthesis method, their shape and size. Recently, the green synthesis route has gained a lot of interest as an alternative environmentally friendly method, resulting in production of effective antimicrobial and antifungal nanoparticles. Unfortunately, as is the case with antibiotics, emerging bacterial resistance against cerium-derived nanoparticles is a growing concern, especially in the case of bacterial biofilm. However, diverse strategies resulting from better understanding of the biology of cerium are promising. The aim of this paper is to present the progress to date in the use of cerium compounds as antimicrobials in clinical applications (in particular wound healing) and to provide an overview of the mechanisms of action of cerium at both the cellular and molecular level. Full article
(This article belongs to the Special Issue Recent Advances in Antimicrobial Materials)
14 pages, 3940 KB  
Review
Covalent Reversible Inhibitors of Cysteine Proteases Containing the Nitrile Warhead: Recent Advancement in the Field of Viral and Parasitic Diseases
by Simone Brogi, Roberta Ibba, Sara Rossi, Stefania Butini, Vincenzo Calderone, Sandra Gemma and Giuseppe Campiani
Molecules 2022, 27(8), 2561; https://doi.org/10.3390/molecules27082561 - 15 Apr 2022
Cited by 35 | Viewed by 7648
Abstract
In the field of drug discovery, the nitrile group is well represented among drugs and biologically active compounds. It can form both non-covalent and covalent interactions with diverse biological targets, and it is amenable as an electrophilic warhead for covalent inhibition. The main [...] Read more.
In the field of drug discovery, the nitrile group is well represented among drugs and biologically active compounds. It can form both non-covalent and covalent interactions with diverse biological targets, and it is amenable as an electrophilic warhead for covalent inhibition. The main advantage of the nitrile group as a warhead is mainly due to its milder electrophilic character relative to other more reactive groups (e.g., -CHO), reducing the possibility of unwanted reactions that would hinder the development of safe drugs, coupled to the ease of installation through different synthetic approaches. The covalent inhibition is a well-assessed design approach for serine, threonine, and cysteine protease inhibitors. The mechanism of hydrolysis of these enzymes involves the formation of a covalent acyl intermediate, and this mechanism can be exploited by introducing electrophilic warheads in order to mimic this covalent intermediate. Due to the relevant role played by the cysteine protease in the survival and replication of infective agents, spanning from viruses to protozoan parasites, we will review the most relevant and recent examples of protease inhibitors presenting a nitrile group that have been introduced to form or to facilitate the formation of a covalent bond with the catalytic cysteine active site residue. Full article
(This article belongs to the Special Issue Covalent Inhibitors in Drug Discovery and Chemical Biology)
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17 pages, 2836 KB  
Review
Excited-State Intramolecular Proton Transfer Dyes with Dual-State Emission Properties: Concept, Examples and Applications
by Timothée Stoerkler, Thibault Pariat, Adèle D. Laurent, Denis Jacquemin, Gilles Ulrich and Julien Massue
Molecules 2022, 27(8), 2443; https://doi.org/10.3390/molecules27082443 - 10 Apr 2022
Cited by 99 | Viewed by 6631
Abstract
Dual-state emissive (DSE) fluorophores are organic dyes displaying fluorescence emission both in dilute and concentrated solution and in the solid-state, as amorphous, single crystal, polycrystalline samples or thin films. This comes in contrast to the vast majority of organic fluorescent dyes which typically [...] Read more.
Dual-state emissive (DSE) fluorophores are organic dyes displaying fluorescence emission both in dilute and concentrated solution and in the solid-state, as amorphous, single crystal, polycrystalline samples or thin films. This comes in contrast to the vast majority of organic fluorescent dyes which typically show intense fluorescence in solution but are quenched in concentrated media and in the solid-state owing to π-stacking interactions; a well-known phenomenon called aggregation-caused quenching (ACQ). On the contrary, molecular rotors with a significant number of free rotations have been engineered to show quenched emission in solution but strong fluorescence in the aggregated-state thanks to restriction of the intramolecular motions. This is the concept of aggregation-induced emission (AIE). DSE fluorophores have been far less explored despite the fact that they are at the crossroad of ACQ and AIE phenomena and allow targeting applications both in solution (bio-conjugation, sensing, imaging) and solid-state (organic electronics, data encryption, lasing, luminescent displays). Excited-State Intramolecular Proton Transfer (ESIPT) fluorescence is particularly suitable to engineer DSE dyes. Indeed, ESIPT fluorescence, which relies on a phototautomerism between normal and tautomeric species, is characterized by a strong emission in the solid-state along with a large Stokes’ shift, an enhanced photostability and a strong sensitivity to the close environment, a feature prone to be used in bio-sensing. A drawback that needs to be overcome is their weak emission intensity in solution, owing to detrimental molecular motions in the excited-state. Several strategies have been proposed in that regard. In the past few years, a growing number of examples of DSE-ESIPT dyes have indeed emerged in the literature, enriching the database of such attractive dyes. This review aims at a brief but concise overview on the exploitation of ESIPT luminescence for the optimization of DSE dyes properties. In that perspective, a synergistic approach between organic synthesis, fluorescence spectroscopy and ab initio calculations has proven to be an efficient tool for the construction and optimization of DSE-ESIPT fluorophores. Full article
(This article belongs to the Special Issue Photoinduced Proton Transfer Processes Within Heterocyclic Structures)
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12 pages, 2337 KB  
Article
Interaction Structure and Affinity of Zwitterionic Amino Acids with Important Metal Cations (Cd2+, Cu2+, Fe3+, Hg2+, Mn2+, Ni2+ and Zn2+) in Aqueous Solution: A Theoretical Study
by Xinning Liu, Menghan Wu, Chenchen Li, Peng Yu, Shanshan Feng, Yanwei Li and Qingzhu Zhang
Molecules 2022, 27(8), 2407; https://doi.org/10.3390/molecules27082407 - 8 Apr 2022
Cited by 37 | Viewed by 4407
Abstract
Heavy metals are non-biodegradable and carcinogenic pollutants with great bio-accumulation potential. Their ubiquitous occurrence in water and soils has caused serious environmental concerns. Effective strategies that can eliminate the heavy metal pollution are urgently needed. Here the adsorption potential of seven heavy metal [...] Read more.
Heavy metals are non-biodegradable and carcinogenic pollutants with great bio-accumulation potential. Their ubiquitous occurrence in water and soils has caused serious environmental concerns. Effective strategies that can eliminate the heavy metal pollution are urgently needed. Here the adsorption potential of seven heavy metal cations (Cd2+, Cu2+, Fe3+, Hg2+, Mn2+, Ni2+ and Zn2+) with 20 amino acids was systematically investigated with Density Functional Theory method. The binding energies calculated at B3LYP-D3/def2TZVP level showed that the contribution order of amino acid side chains to the binding affinity was carboxyl > benzene ring > hydroxyl > sulfhydryl > amino group. The affinity order was inversely proportional to the radius and charge transfer of heavy metal cations, approximately following the order of: Ni2+ > Fe3+ > Cu2+ > Hg2+ > Zn2+ > Cd2+ > Mn2+. Compared to the gas-phase in other researches, the water environment has a significant influence on structures and binding energies of the heavy metal and amino acid binary complexes. Collectively, the present results will provide a basis for the design of a chelating agent (e.g., adding carboxyl or a benzene ring) to effectively remove heavy metals from the environment. Full article
(This article belongs to the Section Computational and Theoretical Chemistry)
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11 pages, 10968 KB  
Article
Synthesis and Reactivity of Manganese Complexes Bearing Anionic PNP- and PCP-Type Pincer Ligands toward Nitrogen Fixation
by Shogo Kuriyama, Shenglan Wei, Takeru Kato and Yoshiaki Nishibayashi
Molecules 2022, 27(7), 2373; https://doi.org/10.3390/molecules27072373 - 6 Apr 2022
Cited by 5 | Viewed by 4154
Abstract
A series of manganese complexes bearing an anionic pyrrole-based PNP-type pincer ligand and an anionic benzene-based PCP-type pincer ligand is synthesized and characterized. The reactivity of these complexes toward ammonia formation and silylamine formation from dinitrogen under mild conditions is evaluated to produce [...] Read more.
A series of manganese complexes bearing an anionic pyrrole-based PNP-type pincer ligand and an anionic benzene-based PCP-type pincer ligand is synthesized and characterized. The reactivity of these complexes toward ammonia formation and silylamine formation from dinitrogen under mild conditions is evaluated to produce only stoichiometric amounts of ammonia and silylamine, probably because the manganese pincer complexes are unstable under reducing conditions. Full article
(This article belongs to the Special Issue Design Strategies for Metal Complexes that Activate Bio-Related Small Molecules)
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20 pages, 5892 KB  
Article
An Expeditious Approach towards the Synthesis and Application of Water-Soluble and Photostable Fluorogenic Chromones for DNA Detection
by Steve Vincent, Suman Mallick, Guillaume Barnoin, Hoang-Ngoan Le, Benoît Y. Michel and Alain Burger
Molecules 2022, 27(7), 2267; https://doi.org/10.3390/molecules27072267 - 31 Mar 2022
Cited by 3 | Viewed by 2971
Abstract
The intensive research for hybridization probes based on organic molecules with fluorogenic properties is currently attracting particular attention due to their potential to efficiently recognize different DNA conformations and the local environment. However, most established organic chromophores do not meet the requirements of [...] Read more.
The intensive research for hybridization probes based on organic molecules with fluorogenic properties is currently attracting particular attention due to their potential to efficiently recognize different DNA conformations and the local environment. However, most established organic chromophores do not meet the requirements of this task, as they do not exhibit good brightness in aqueous buffer media, develop aggregation and/or are not easily conjugated to oligodeoxynucleotides (ODNs) while keeping their photophysics intact. Herein, an important modification strategy was employed for a well-known fluorophore, 2-(4-(diethylamino)phenyl)-3-hydroxychromone (dEAF). Although this push–pull dye absorbs intensively in the visible range and shows emission with large Stokes shifts in all organic solvents, it is strongly quenched in water. This Achilles’ heel prompted us to implement a new strategy to obtain a series of dyes that retain all the photophysical features of dEAF in water, conjugate readily with oligonucleotides, and furthermore demonstrate sensitivity to hydration, thus paving the way for a high-performance fluorogenic DNA hybridization probe. Full article
(This article belongs to the Special Issue Fluorescent Probes in Pharmaceutical and Drug Design Applications: Quantum Chemistry-Based Design, Synthesis, Photophysical and Chemical Properties, Biological Applications)
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29 pages, 2169 KB  
Review
Modification of Lipid-Based Nanoparticles: An Efficient Delivery System for Nucleic Acid-Based Immunotherapy
by Chi Zhang, Yifan Ma, Jingjing Zhang, Jimmy Chun-Tien Kuo, Zhongkun Zhang, Haotian Xie, Jing Zhu and Tongzheng Liu
Molecules 2022, 27(6), 1943; https://doi.org/10.3390/molecules27061943 - 17 Mar 2022
Cited by 70 | Viewed by 10865
Abstract
Lipid-based nanoparticles (LBNPs) are biocompatible and biodegradable vesicles that are considered to be one of the most efficient drug delivery platforms. Due to the prominent advantages, such as long circulation time, slow drug release, reduced toxicity, high transfection efficiency, and endosomal escape capacity, [...] Read more.
Lipid-based nanoparticles (LBNPs) are biocompatible and biodegradable vesicles that are considered to be one of the most efficient drug delivery platforms. Due to the prominent advantages, such as long circulation time, slow drug release, reduced toxicity, high transfection efficiency, and endosomal escape capacity, such synthetic nanoparticles have been widely used for carrying genetic therapeutics, particularly nucleic acids that can be applied in the treatment for various diseases, including congenital diseases, cancers, virus infections, and chronic inflammations. Despite great merits and multiple successful applications, many extracellular and intracellular barriers remain and greatly impair delivery efficacy and therapeutic outcomes. As such, the current state of knowledge and pitfalls regarding the gene delivery and construction of LBNPs will be initially summarized. In order to develop a new generation of LBNPs for improved delivery profiles and therapeutic effects, the modification strategies of LBNPs will be reviewed. On the basis of these developed modifications, the performance of LBNPs as therapeutic nanoplatforms have been greatly improved and extensively applied in immunotherapies, including infectious diseases and cancers. However, the therapeutic applications of LBNPs systems are still limited due to the undesirable endosomal escape, potential aggregation, and the inefficient encapsulation of therapeutics. Herein, we will review and discuss recent advances and remaining challenges in the development of LBNPs for nucleic acid-based immunotherapy. Full article
(This article belongs to the Special Issue Application of Novel Method in Pharmaceutical Study II)
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11 pages, 3708 KB  
Article
Iridium(I)-Catalyzed Isoindolinone-Directed Branched-Selective Aromatic C–H Alkylation with Simple Alkenes
by Maoqian Xiong, Yuhang Shu, Jie Tang, Fan Yang and Dong Xing
Molecules 2022, 27(6), 1923; https://doi.org/10.3390/molecules27061923 - 16 Mar 2022
Cited by 5 | Viewed by 4125
Abstract
We report an iridium(I)-catalyzed branched-selective C–H alkylation of N-arylisoindolinones with simple alkenes as the alkylating agents. The amide carbonyl group of the isoindolinone motif acts as the directing group to assist the ortho C–H activation of the N-aryl ring. With this [...] Read more.
We report an iridium(I)-catalyzed branched-selective C–H alkylation of N-arylisoindolinones with simple alkenes as the alkylating agents. The amide carbonyl group of the isoindolinone motif acts as the directing group to assist the ortho C–H activation of the N-aryl ring. With this atom-economic and highly branched-selective protocol, an array of biologically relevant N-arylisoindolinones were obtained in good yields. Asymmetric control was achieved with up to 87:13 er when a BiPhePhos-like chiral ligand was employed. Full article
(This article belongs to the Section Organic Chemistry)
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14 pages, 1014 KB  
Review
The (Bio)Chemistry of Non-Transferrin-Bound Iron
by André M. N. Silva and Maria Rangel
Molecules 2022, 27(6), 1784; https://doi.org/10.3390/molecules27061784 - 9 Mar 2022
Cited by 36 | Viewed by 6928
Abstract
In healthy individuals, virtually all blood plasma iron is bound by transferrin. However, in several diseases and clinical conditions, hazardous non-transferrin-bound iron (NTBI) species occur. NTBI represents a potentially toxic iron form, being a direct cause of oxidative stress in the circulating compartment [...] Read more.
In healthy individuals, virtually all blood plasma iron is bound by transferrin. However, in several diseases and clinical conditions, hazardous non-transferrin-bound iron (NTBI) species occur. NTBI represents a potentially toxic iron form, being a direct cause of oxidative stress in the circulating compartment and tissue iron loading. The accumulation of these species can cause cellular damage in several organs, namely, the liver, spleen, and heart. Despite its pathophysiological relevance, the chemical nature of NTBI remains elusive. This has precluded its use as a clinical biochemical marker and the development of targeted therapies. Herein, we make a critical assessment of the current knowledge of NTBI speciation. The currently accepted hypotheses suggest that NTBI is mostly iron bound to citric acid and iron bound to serum albumin, but the chemistry of this system remains fuzzy. We explore the complex chemistry of iron complexation by citric acid and its implications towards NTBI reactivity. Further, the ability of albumin to bind iron is revised and the role of protein post-translational modifications on iron binding is discussed. The characterization of the NTBI species structure may be the starting point for the development of a standardized analytical assay, the better understanding of these species’ reactivity or the identification of NTBI uptake mechanisms by different cell types, and finally, to the development of new therapies. Full article
(This article belongs to the Special Issue Molecular and Spectroscopic Insights into Metal Ions Speciation in Extracellular Fluids)
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13 pages, 2711 KB  
Article
Investigating the Effects of Amino Acid Variations in Human Menin
by Carmen Biancaniello, Antonia D’Argenio, Deborah Giordano, Serena Dotolo, Bernardina Scafuri, Anna Marabotti, Antonio d’Acierno, Roberto Tagliaferri and Angelo Facchiano
Molecules 2022, 27(5), 1747; https://doi.org/10.3390/molecules27051747 - 7 Mar 2022
Cited by 9 | Viewed by 4645
Abstract
Human menin is a nuclear protein that participates in many cellular processes, as transcriptional regulation, DNA damage repair, cell signaling, cell division, proliferation, and migration, by interacting with many other proteins. Mutations of the gene encoding menin cause multiple endocrine neoplasia type 1 [...] Read more.
Human menin is a nuclear protein that participates in many cellular processes, as transcriptional regulation, DNA damage repair, cell signaling, cell division, proliferation, and migration, by interacting with many other proteins. Mutations of the gene encoding menin cause multiple endocrine neoplasia type 1 (MEN1), a rare autosomal dominant disorder associated with tumors of the endocrine glands. In order to characterize the structural and functional effects at protein level of the hundreds of missense variations, we investigated by computational methods the wild-type menin and more than 200 variants, predicting the amino acid variations that change secondary structure, solvent accessibility, salt-bridge and H-bond interactions, protein thermostability, and altering the capability to bind known protein interactors. The structural analyses are freely accessible online by means of a web interface that integrates also a 3D visualization of the structure of the wild-type and variant proteins. The results of the study offer insight into the effects of the amino acid variations in view of a more complete understanding of their pathological role. Full article
(This article belongs to the Special Issue Molecular Simulations Applications in Biochemistry and Molecular Biology)
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55 pages, 83405 KB  
Review
Sulforaphane and Its Bifunctional Analogs: Synthesis and Biological Activity
by Łukasz Janczewski
Molecules 2022, 27(5), 1750; https://doi.org/10.3390/molecules27051750 - 7 Mar 2022
Cited by 68 | Viewed by 9599
Abstract
For decades, various plants have been studied as sources of biologically active compounds. Compounds with anticancer and antimicrobial properties are the most frequently desired. Cruciferous plants, including Brussels sprouts, broccoli, and wasabi, have a special role in the research studies. Studies have shown [...] Read more.
For decades, various plants have been studied as sources of biologically active compounds. Compounds with anticancer and antimicrobial properties are the most frequently desired. Cruciferous plants, including Brussels sprouts, broccoli, and wasabi, have a special role in the research studies. Studies have shown that consumption of these plants reduce the risk of lung, breast, and prostate cancers. The high chemopreventive and anticancer potential of cruciferous plants results from the presence of a large amount of glucosinolates, which, under the influence of myrosinase, undergo an enzymatic transformation to biologically active isothiocyanates (ITCs). Natural isothiocyanates, such as benzyl isothiocyanate, phenethyl isothiocyanate, or the best-tested sulforaphane, possess anticancer activity at all stages of the carcinogenesis process, show antibacterial activity, and are used in organic synthesis. Methods of synthesis of sulforaphane, as well as its natural or synthetic bifunctional analogues with sulfinyl, sulfanyl, sulfonyl, phosphonate, phosphinate, phosphine oxide, carbonyl, ester, carboxamide, ether, or additional isothiocyanate functional groups, and with the unbranched alkyl chain containing 2–6 carbon atoms, are discussed in this review. The biological activity of these compounds are also reported. In the first section, glucosinolates, isothiocyanates, and mercapturic acids (their metabolites) are briefly characterized. Additionally, the most studied anticancer and antibacterial mechanisms of ITC actions are discussed. Full article
(This article belongs to the Special Issue Featured Reviews in Organic Chemistry)
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23 pages, 3936 KB  
Review
New Halogen-Containing Drugs Approved by FDA in 2021: An Overview on Their Syntheses and Pharmaceutical Use
by Davide Benedetto Tiz, Luana Bagnoli, Ornelio Rosati, Francesca Marini, Luca Sancineto and Claudio Santi
Molecules 2022, 27(5), 1643; https://doi.org/10.3390/molecules27051643 - 2 Mar 2022
Cited by 116 | Viewed by 18187
Abstract
This review describes the recent Food and Drug Administration (FDA)-approved drugs (in the year 2021) containing at least one halogen atom (covalently bound). The structures proposed throughout this work are grouped according to their therapeutical use. Their synthesis is presented as well. The [...] Read more.
This review describes the recent Food and Drug Administration (FDA)-approved drugs (in the year 2021) containing at least one halogen atom (covalently bound). The structures proposed throughout this work are grouped according to their therapeutical use. Their synthesis is presented as well. The number of halogenated molecules that are reaching the market is regularly preserved, and 14 of the 50 molecules approved by the FDA in the last year contain halogens. This underlines the emergent role of halogens and, in particular, of fluorine and chlorine in the preparation of drugs for the treatment of several diseases such as viral infections, several types of cancer, cardiovascular disease, multiple sclerosis, migraine and inflammatory diseases such as vasculitis. Full article
(This article belongs to the Special Issue Featured Reviews in Organic Chemistry)
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29 pages, 6922 KB  
Article
Tuning Photophysical Properties by p-Functional Groups in Zn(II) and Cd(II) Complexes with Piperonylic Acid
by Francisco Sánchez-Férez, Joaquim Mª Rius-Bartra, José A. Ayllón, Teresa Calvet, Mercè Font-Bardia and Josefina Pons
Molecules 2022, 27(4), 1365; https://doi.org/10.3390/molecules27041365 - 17 Feb 2022
Cited by 17 | Viewed by 3442
Abstract
Aggregation between discrete molecules is an essential factor to prevent aggregation-caused quenching (ACQ). Indeed, functional groups capable of generating strong hydrogen bonds are likely to assemble and cause ACQ and photoinduced electron transfer processes. Thus, it is possible to compare absorption and emission [...] Read more.
Aggregation between discrete molecules is an essential factor to prevent aggregation-caused quenching (ACQ). Indeed, functional groups capable of generating strong hydrogen bonds are likely to assemble and cause ACQ and photoinduced electron transfer processes. Thus, it is possible to compare absorption and emission properties by incorporating two ligands with a different bias toward intra- and intermolecular interactions that can induce a specific structural arrangement. In parallel, the π electron-donor or electron-withdrawing character of the functional groups could modify the Highest Ocuppied Molecular Orbital (HOMO)–Lowest Unocuppied Molecular Orbital (LUMO) energy gap. Reactions of M(OAc)2·2H2O (M = Zn(II) and Cd(II); OAc = acetate) with 1,3-benzodioxole-5-carboxylic acid (Piperonylic acid, HPip) and 4-acetylpyridine (4-Acpy) or isonicotinamide (Isn) resulted in the formation of four complexes. The elucidation of their crystal structure showed the formation of one paddle-wheel [Zn(μ-Pip)2(4-Acpy)]2 (1); a mixture of one dimer and two monomers [Zn(µ-Pip)(Pip)(Isn)2]2·2[Zn(Pip)2(HPip)(Isn)]·2MeOH (2); and two dimers [Cd(μ-Pip)(Pip)(4-Acpy)2]2 (3) and [Cd(μ-Pip)(Pip)(Isn)2]2·MeOH (4). They exhibit bridged (1, µ2-η1:η1), bridged, chelated and monodentated (2, µ2-η1:η1, µ1-η1:η1 and µ1-η1), or simultaneously bridged and chelated (3 and 4, µ2-η2:η1) coordination modes. Zn(II) centers accommodate coordination numbers 5 and 6, whereas Cd(II) presents coordination number 7. We have related their photophysical properties and fluorescence quantum yields with their geometric variations and interactions supported by TD-DFT calculations. Full article
(This article belongs to the Special Issue Nitrogen Ligands)
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29 pages, 26357 KB  
Review
The Choice of Rhodium Catalysts in [2+2+2] Cycloaddition Reaction: A Personal Account
by Anna Pla-Quintana and Anna Roglans
Molecules 2022, 27(4), 1332; https://doi.org/10.3390/molecules27041332 - 16 Feb 2022
Cited by 21 | Viewed by 4048
Abstract
[2+2+2] Cycloaddition reaction is a captivating process that assembles six-membered rings from three unsaturations with complete atom economy. Of the multiple transition metals that can be used to catalyze this reaction, rhodium offers many advantages. These include high activity and versatility, but especially [...] Read more.
[2+2+2] Cycloaddition reaction is a captivating process that assembles six-membered rings from three unsaturations with complete atom economy. Of the multiple transition metals that can be used to catalyze this reaction, rhodium offers many advantages. These include high activity and versatility, but especially the ability to easily tune the reactivity and selectivity by the modification of the ligands around the metal. In this personal account, we summarize our endeavours in the development of efficient and sustainable [2+2+2] cycloaddition reactions to prepare products of interest, develop conditions in which the catalyst can be recovered and reused, and understand the mechanistic details that govern the selectivity of the processes. Full article
(This article belongs to the Special Issue Organic Chemistry, Synthesis, and Catalysis: Special Issue in Memory of Professor Victor Snieckus for His Outstanding Contributions to Organic Chemistry)
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15 pages, 12257 KB  
Article
Photoinduced Bisphosphination of Alkynes with Phosphorus Interelement Compounds and Its Application to Double-Bond Isomerization
by Yuki Yamamoto, Ryo Tanaka, Shintaro Kodama, Akihiro Nomoto and Akiya Ogawa
Molecules 2022, 27(4), 1284; https://doi.org/10.3390/molecules27041284 - 14 Feb 2022
Cited by 8 | Viewed by 3229
Abstract
The addition of interelement compounds with heteroatom-heteroatom single bonds to carbon-carbon unsaturated bonds under light irradiation is believed to be an atomically efficient method to procure materials with carbon-heteroatom bonds. In this study, we achieved the photoinduced bisphosphination of alkynes using the phosphorus [...] Read more.
The addition of interelement compounds with heteroatom-heteroatom single bonds to carbon-carbon unsaturated bonds under light irradiation is believed to be an atomically efficient method to procure materials with carbon-heteroatom bonds. In this study, we achieved the photoinduced bisphosphination of alkynes using the phosphorus interelement compound, tetraphenyldiphosphine monosulfide (1), to stereoselectively obtain the corresponding (E)-vic-1,2-bisphosphinoalkenes, which are important transition-metal ligands. The bisphosphination reaction was performed by mixing 1 and various alkynes and then exposing the mixture to light irradiation. Optimization of the conditions for the bisphosphination reaction resulted in a wide substrate range and excellent trans-selectivity. Moreover, the completely regioselective introduction of pentavalent and trivalent phosphorus groups to the terminal and internal positions of the alkynes, respectively, was achieved. We also found that the novel double-bond isomerization reaction of the synthesized bisphosphinated products occurred with a catalytic amount of a base under mild conditions. Our method for the photoinduced bisphosphination of carbon-carbon unsaturated compounds may have strong implications for both organic synthesis and organometallic and catalyst chemistry. Full article
(This article belongs to the Special Issue Modern Organophosphorus Chemistry)
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19 pages, 8596 KB  
Article
Identification of a Common Pharmacophore for Binding to MMP2 and RGD Integrin: Towards a Multitarget Approach to Inhibit Cancer Angiogenesis and Metastasis
by Lorenzo Baldini, Elena Lenci, Francesca Bianchini and Andrea Trabocchi
Molecules 2022, 27(4), 1249; https://doi.org/10.3390/molecules27041249 - 12 Feb 2022
Cited by 5 | Viewed by 4019
Abstract
During tumor angiogenesis different growth factors, cytokines and other molecules interact closely with each other to facilitate tumor cell invasion and metastatic diffusion. The most intensively studied as molecular targets in anti-angiogenic therapies are vascular endothelial growth factor (VEGF) and related receptors, integrin [...] Read more.
During tumor angiogenesis different growth factors, cytokines and other molecules interact closely with each other to facilitate tumor cell invasion and metastatic diffusion. The most intensively studied as molecular targets in anti-angiogenic therapies are vascular endothelial growth factor (VEGF) and related receptors, integrin receptors and matrix metalloproteinases (MMPs). Considering the poor efficacy of cancer angiogenesis monotherapies, we reasoned combining the inhibition of αvβ3 and MMP2 as a multitarget approach to deliver a synergistic blockade of tumor cell migration, invasion and metastasis. Accordingly, we identified a common pharmacophore in the binding cavity of MMP2 and αvβ3, demonstrating such approach with the design, synthesis and bioassays of tyrosine-derived peptidomimetics carrying the necessary functional groups to bind to key pharmacophoric elements of MMP2 and αvβ3 RGD integrin. Full article
(This article belongs to the Special Issue Featured Papers in Medicinal Chemistry)
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