Chemistry

19 pages, 4738 KiB

Open AccessArticle

An Extensive Study of the Production of Hydrogen by Cellulose and Lignin Pyrolysis Using Rhenium-Based Catalysts

by Mizraim Guillermo Granados-Fitch, Juan Manuel Quintana-Melgoza, Erick Adrian Juarez-Arellano and Miguel Avalos-Borja

Chemistry 2025, 7(2), 33; https://doi.org/10.3390/chemistry7020033 (registering DOI) - 1 Mar 2025

Abstract

The use of rhenium-based catalysts (Re₂C, Re₃B, ReB₂, and ReS₂) obtained by mechanosynthesis in the pyrolysis of cellulose and lignin from 500 to 800 °C using 10 and 20 wt.% of catalysts is reported. The [...] Read more.

The use of rhenium-based catalysts (Re₂C, Re₃B, ReB₂, and ReS₂) obtained by mechanosynthesis in the pyrolysis of cellulose and lignin from 500 to 800 °C using 10 and 20 wt.% of catalysts is reported. The mechanosynthesis of ReS₂ has been reported for the first time. The catalytic pyrolysis of cellulose resulted in maximum H₂ production at 800 °C and 10 wt.% catalyst, with 44% H₂ yield using a Re₃B catalyst. In contrast, lignin catalytic pyrolysis also showed maximum production under the same conditions, with an 86.1% H₂ yield using the NiO/SiO₂ catalyst; however, the catalyst did not drastically enhance H₂ production. H₂ formation by cellulose pyrolysis is a thermocatalytic process, whereas lignin pyrolysis is an entirely thermic process. A reaction mechanism was proposed to explain the H₂ formation by both catalytic cellulose and lignin pyrolysis. Full article

(This article belongs to the Section Catalysis)

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10 pages, 3623 KiB

Open AccessArticle

Solid–Liquid Phase Transition-Induced Magnetic Property Changes in Tetrakis(ethylthio)tetrathiafulvalene Radical Cation Salt

by Toshihiro Sakai, Soichiro Kawamorita, Takeshi Naota and Shuichi Suzuki

Chemistry 2025, 7(2), 32; https://doi.org/10.3390/chemistry7020032 (registering DOI) - 1 Mar 2025

Abstract

We discovered that the radical cation salt [1^•+][NTf₂⁻], composed of tetrakis(ethylthio)tetrathiafulvalene radical cation and bis(N-trifluoromethanesulfonyl)imide ion, exhibits significant changes in its magnetic properties during a solid–liquid phase transition. Single-crystal structure analysis revealed that the radical [...] Read more.

We discovered that the radical cation salt [1^•+][NTf₂⁻], composed of tetrakis(ethylthio)tetrathiafulvalene radical cation and bis(N-trifluoromethanesulfonyl)imide ion, exhibits significant changes in its magnetic properties during a solid–liquid phase transition. Single-crystal structure analysis revealed that the radical cation salt [1^•+][NTf₂⁻] forms an associated structure called a π-dimer in the crystalline phase. The extremely weak ESR signal in the crystalline state indicates strong antiferromagnetic interactions between unpaired electrons within the π-dimer. Upon heating, the crystalline phase transitions into a liquid state without decomposition at 144 °C (417 K). The ESR signals in the liquid state are significantly stronger than those in the solid state, suggesting the formation of a paramagnetic state with weak interactions between radical cations. Full article

(This article belongs to the Special Issue Open-Shell Systems—a Memorial Issue Dedicated to Professor Masayoshi Nakano)

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14 pages, 1995 KiB

Open AccessArticle

Computational Design and Synthesis of Phthalimide Derivatives as TGF-β Pathway Inhibitors for Cancer Therapeutics

by Héctor M. Heras-Martínez, Blanca Sánchez-Ramírez, Linda-Lucila Landeros-Martínez, Víctor H. Ramos-Sánchez, Alejandro A. Camacho-Dávila, Kostiantyn O. Marichev, Alejandro Bugarin and David Chávez-Flores

Chemistry 2025, 7(2), 31; https://doi.org/10.3390/chemistry7020031 - 26 Feb 2025

Abstract

Background: This study investigates the synthesis and pharmacological potential of N-substituted isoindoline-1,3-dione (phthalimide) derivatives. Using the M06 meta-GGA hybrid functional with a polarized 6-311G(d,p) basis set, computational evaluations assessed their impact on apoptosis modulation in colon cancer cells. Molecular docking studies targeted [...] Read more.

Background: This study investigates the synthesis and pharmacological potential of N-substituted isoindoline-1,3-dione (phthalimide) derivatives. Using the M06 meta-GGA hybrid functional with a polarized 6-311G(d,p) basis set, computational evaluations assessed their impact on apoptosis modulation in colon cancer cells. Molecular docking studies targeted the TGF-β protein (PDB: 1RW8) at the ALK5 binding site. On this study fourteen molecules were evaluated (P1–P14) and six (P1, P3, P4, P5, P7, and P13) demonstrated promising binding values. Methods: from the fourteen studied compounds five compounds (P2, P4, P7, P10, and P11) were successfully synthesized and fully characterized. The reactions were monitored via TLC and HPLC confirming high-purity compounds. Functional groups were identified through FTIR and structural characterization was supported by NMR analyses. Results: Density functional theory calculations and docking simulations allowed to classified the compounds as potential ALK5 inhibitors. Synthesized derivatives were developed in yields from 85 to 99% and showed better binding affinities than Capecitabine (−6.95 kcal/mol) used as control compound, with P7 (5-hydroxy-4-oxo-2-phenyl-4H-chromen-7-yl 2-(1,3-dioxoisoindolin-2-yl) acetate) leading the group with a binding energy of −12.28 kcal/mol. Other synthesized compounds also exhibited significant affinities: P4 (−11.42 kcal/mol), P10 (−8.99 kcal/mol), P11 (−7.50 kcal/mol), and P2 (−7.22 kcal/mol). Conclusions: Integrating computational insights with experimental validation highlights the therapeutic potential of phthalimide derivatives, particularly P7. The study underscores a rigorous approach to identifying promising candidates for anticancer therapeutics, warranting further exploration. Full article

(This article belongs to the Special Issue Cutting-Edge Studies of Computational Approaches in Drug Discovery)

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16 pages, 16198 KiB

Open AccessArticle

Effects of Substituent and Scaffold Changes on the Inhibition of Human P5C Reductase by Phenyl-Substituted Aminomethylene Bisphosphonates

by Giuseppe Forlani

Chemistry 2025, 7(2), 30; https://doi.org/10.3390/chemistry7020030 - 25 Feb 2025

Abstract

Being overexpressed in many cancer types and related to tumor invasiveness, the activity of P5C reductase represents a promising target for cancer therapy, yet no effective inhibitors have been identified so far. Several phenyl-substituted aminomethylenebisphosphonic acids had been found to inhibit the plant [...] Read more.

Being overexpressed in many cancer types and related to tumor invasiveness, the activity of P5C reductase represents a promising target for cancer therapy, yet no effective inhibitors have been identified so far. Several phenyl-substituted aminomethylenebisphosphonic acids had been found to inhibit the plant enzyme in the micro- to millimolar range. The two most active compounds were previously shown to be remarkably active against human P5C reductase (PYCR1, gene ID 5831). To investigate their structure–activity relationships, the human enzyme was heterogously expressed in E. coli, affinity purified and assayed in the presence of increasing concentrations of various aminobisphosphonates differing in substituents on the phenyl ring, using either NADH or NADPH as the electron donor. Some analogues, namely aminoethylenebisphosphonates, hydroxybisphosphonates, aminophosphonates and hydroxyphosphonates, were also evaluated. Results allowed to define the chemical features required for effective inhibition. The aminobisphosphonic moiety was found essential for activity, which was enhanced by the presence of electron-withdrawing substituents on the phenyl ring, provided that an optimal steric hindrance is not exceeded. These results could open up new perspectives on the synthesis of effective inhibitors of human P5C reductase to be used in chemotherapy. Full article

(This article belongs to the Section Medicinal Chemistry)

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36 pages, 4825 KiB

Open AccessReview

Packed Bed Microreactors for Sustainable Chemistry and Process Development

by Lu Zhang and Jun Yue

Chemistry 2025, 7(2), 29; https://doi.org/10.3390/chemistry7020029 - 24 Feb 2025

Abstract

Microreactor technology is seen as a promising approach to achieve green and sustainable synthesis in chemical fields because of the significant process intensification and fine control over reaction parameters caused by the miniaturization of reactor scale. The incorporation of solid catalysts as a [...] Read more.

Microreactor technology is seen as a promising approach to achieve green and sustainable synthesis in chemical fields because of the significant process intensification and fine control over reaction parameters caused by the miniaturization of reactor scale. The incorporation of solid catalysts as a packed bed in microreactors opens numerous opportunities for the efficient heterogeneous catalysis that plays a pivotal role in many industrially relevant chemical processes. In this review, the recent development in the use of packed bed microreactors as a versatile research tool and intensified production unit will be highlighted in the application areas including the synthesis of valuable chemicals and fuels, high-throughput catalyst screening, and kinetic/chemistry investigation. Selected reaction examples involving different reactant phases and catalyst categories will be particularly discussed, with an emphasis on the reactor performance in relation to the fundamental chemistry and engineering principles under microflow. In the end, future challenges and the outlook of packed bed microreactors for sustainable chemistry and process development will be provided. Full article

(This article belongs to the Special Issue A Themed Issue in Honor of Professor George Whitesides on the Occasion of His 85th Birthday Anniversary)

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16 pages, 3603 KiB

Open AccessArticle

Synthesis of Terbenzo- and Tetrabenzoolympicenyl Radicals and Their Cations

by Zewen Guo, Xiaoqi Tian and Zhe Sun

Chemistry 2025, 7(2), 28; https://doi.org/10.3390/chemistry7020028 - 24 Feb 2025

Abstract

The synthesis of two polycyclic aromatic hydrocarbon (PAH) monoradicals, terbenzoolympicenyl radical (BOR1) and tetrabenzoolympicenyl radical (BOR2), is reported. One-electron oxidation of both BOR1 and BOR2 yielded stable cationic species BOR1+ and BOR2+, whose structures were unambiguously characterized using [...] Read more.

The synthesis of two polycyclic aromatic hydrocarbon (PAH) monoradicals, terbenzoolympicenyl radical (BOR1) and tetrabenzoolympicenyl radical (BOR2), is reported. One-electron oxidation of both BOR1 and BOR2 yielded stable cationic species BOR1+ and BOR2+, whose structures were unambiguously characterized using 2D nuclear magnetic resonance (NMR) spectroscopy. The physical properties of BOR1 and BOR2 were investigated by means of electron paramagnetic resonance (EPR), UV-vis-NIR, cyclic voltammetry (CV), and density functional theory (DFT) calculations. BOR1+ and BOR2+ exhibited intense near-infrared (NIR) absorption, which may be of potential use in the biological fields. Full article

(This article belongs to the Special Issue Open-Shell Systems—a Memorial Issue Dedicated to Professor Masayoshi Nakano)

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9 pages, 2847 KiB

Open AccessCommunication

Crystalline Diradical Dianions and Radical Anions of Indenofluorenediones

by Xue Dong, Tao Wang, Yu Zhao, Quanchun Sun, Shuxuan Tang, Yue Zhao and Xinping Wang

Chemistry 2025, 7(1), 27; https://doi.org/10.3390/chemistry7010027 - 19 Feb 2025

Abstract

Fluorenone derivatives represent promising candidates for electron-transport materials in organic electronic devices. Given that anionic species serve as electron-transfer carriers in electron-transport materials, it is highly desirable to isolate and characterize the radical anions and dianions of indenofluorened derivatives (IFO). In this work, [...] Read more.

Fluorenone derivatives represent promising candidates for electron-transport materials in organic electronic devices. Given that anionic species serve as electron-transfer carriers in electron-transport materials, it is highly desirable to isolate and characterize the radical anions and dianions of indenofluorened derivatives (IFO). In this work, the reduction of three indenofluorenedione derivatives (IFO, 1, 2 and 3) with potassium resulted in three radical anion salts (1K[(crypt-222)], 2K[(crypt-222)] and 3K) and one dianion salt (2[K(crypt-222)]₂). Single-crystal X-ray diffraction and electron paramagnetic resonance (EPR) spectroscopy reveal that 1K[(crypt-222)] and 2K[(crypt-222)] have a full delocalization of the unpaired electron which is supported by calculated spin density distributions. We demonstrate that the polarization of electron spin in 3K is induced by potassium ion coordination through single-crystal X-ray structure analysis and DFT calculations, suggesting the electrostatic effect by potassium ion has a significant influence on the spin density modulation. Superconducting quantum interference device (SQUID) measurements and DFT calculations show that 2[K(crypt-222)]₂ has an open-shell singlet base with a large singlet-triplet energy gap (ΔE_os-t = −7.40 kcal mol⁻¹) so that the excited triplet state is not accessible at room temperature. Full article

(This article belongs to the Special Issue Open-Shell Systems—a Memorial Issue Dedicated to Professor Masayoshi Nakano)

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19 pages, 11004 KiB

Open AccessArticle

The Influence of Electron Beam Irradiation on the Performance of Hydrogenation Catalysts Containing Co and Carboneous Particles on Silica

by Mykola I. Arabadzhy, Vyacheslav P. Pashkevych, Olena O. Pariiska, Oleksiy V. Melnychenko, Volodymyr V. Buryanov, Vladyslav V. Subotin, Bohdan V. Vashchenko, Eugeniy M. Ostapchuk, Andriy I. Frolov, Konstantin S. Gavrilenko, Serhiy V. Ryabukhin, Dmytro M. Volochnyuk and Sergey V. Kolotilov

Chemistry 2025, 7(1), 26; https://doi.org/10.3390/chemistry7010026 - 19 Feb 2025

Abstract

This study was aimed at elucidating the role of the carboneous component in Co–carbon-containing catalysts for the hydrogenation of organic compounds. A Co-C/SiO₂ catalyst was synthesized via pyrolysis of a Co(II) complex with 1,2-diaminobenzene on silica and subsequently irradiated with 2.3 MeV [...] Read more.

This study was aimed at elucidating the role of the carboneous component in Co–carbon-containing catalysts for the hydrogenation of organic compounds. A Co-C/SiO₂ catalyst was synthesized via pyrolysis of a Co(II) complex with 1,2-diaminobenzene on silica and subsequently irradiated with 2.3 MeV electrons, producing Co-C/SiO₂*. A comprehensive characterization using XRD, TEM, IR, and Raman spectroscopy indicated minimal structural changes in the cobalt nanoparticles and carboneous materials. However, the Raman analysis revealed a slight decrease in the structural defect content in the carboneous component upon irradiation, which could occur due to defect healing. The catalytic tests, including the hydrogenation of 26 compounds, demonstrated an enhanced performance of the irradiated catalyst in 17 cases. This performance improvement was attributed to a modification of the carboneous material. It could be concluded that the carboneous components in Co-C composites contributed to their catalytic performance, probably by modifying the electronic structure of Co nanoparticles. In turn, the results provide arguments against the supposition that hydrogenation occurs on the structural defects of the carboneous material. Full article

(This article belongs to the Section Catalysis)

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17 pages, 2267 KiB

Open AccessArticle

Simulating Analyte Extraction via Sorption in Powdered and Lyophilized Pharmaceutical Products Using Butyl Rubbers

by Nikolaos Kritikos, Anna Bletsou, Constantinos Kousoulos and Yannis Dotsikas

Chemistry 2025, 7(1), 25; https://doi.org/10.3390/chemistry7010025 - 18 Feb 2025

Abstract

A novel extraction method based on solid-to-solid interactions has been developed to investigate the acquisition of contaminants from butyl rubber materials, with potential applications in the pharmaceutical industry. The extraction medium used is silica gel—a cost-effective, non-toxic, heat-resistant, and chemically inert material that [...] Read more.

A novel extraction method based on solid-to-solid interactions has been developed to investigate the acquisition of contaminants from butyl rubber materials, with potential applications in the pharmaceutical industry. The extraction medium used is silica gel—a cost-effective, non-toxic, heat-resistant, and chemically inert material that is easy to handle in laboratory settings. Silica gel also enables straightforward recovery of adsorbed species using standard laboratory solvents. This method effectively exhausts contaminants from typical rubber articles within a reasonable timeframe, even under ambient conditions, while preserving the integrity of the material. Unlike traditional destructive liquid-based extractions, this approach produces significantly cleaner chromatographic profiles. This study focuses on the primary analytes extracted from chlorobutyl rubber, including halogenated rubber volatile impurities (VOIs), and tracks their acquisition over the course of the experiment. The findings provide valuable insights into the diffusion-based process by which pharmaceutical powders acquire contaminants, spanning a wide range of volatility and lipophilicity. Full article

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18 pages, 1166 KiB

Open AccessArticle

Chemical and Biological Investigation of Ceiba chodatii Hassl. Flowers

by Engy Saadalah Ibrahem, John Refaat Fahim, Mamdouh Nabil Samy, Ahmed G. Darwish, Samar Yehia Desoukey, Mohamed Salah Kamel and Samir A. Ross

Chemistry 2025, 7(1), 24; https://doi.org/10.3390/chemistry7010024 - 12 Feb 2025

Abstract

Ceiba (syn. Chorisia) trees have attracted multifaceted attention not only due to their ornamental and economic value but also for their remarkable metabolic diversity and therapeutic properties. In view of that, this work explores the chemical composition of Ceiba chodatii Hassl. and [...] Read more.

Ceiba (syn. Chorisia) trees have attracted multifaceted attention not only due to their ornamental and economic value but also for their remarkable metabolic diversity and therapeutic properties. In view of that, this work explores the chemical composition of Ceiba chodatii Hassl. and its biological potential. Overall, GC–MS-based analysis of the lipoidal constituents of C. chodatii flowers revealed the presence of diverse classes of metabolites that were dominated by long-chain aliphatic esters (77.016%), ketones (6.396%), aliphatic hydrocarbons (5.757%), fatty alcohols (3.718%), aromatic acid esters (2.794%), alkylamides (1.58%), aldehydes (1.035%), aromatic hydrocarbons (0.31%), and ethers (0.29%). In addition, repeated chromatographic fractionation of different fractions of the total alcoholic extract of the flowers afforded 13 metabolites of varied structural types, including fatty esters and alcohols, phytosterols, monoglycerides, furanoids, and flavonoid glycosides. Structures of the obtained compounds were determined by different spectroscopic techniques, such as 1H- and 13C-NMR, APT, DEPT, and EI–MS analyses. Noteworthily, a wide range of the metabolites identified herein using different analytical approaches were described for the first time in the plant species under study or in those belonging to the genus Ceiba. Finally, the total extract and different fractions of C. chodatii flowers as well as the isolated flavonoids showed weak anti-infective potential against a group of human pathogens at concentration ranges up to 200 and 20 µg/mL, respectively. In contrast, the total extract and different fractions of the flowers exerted mild to moderate anti-proliferative activities against MDA-MB-468 cells, with IC₅₀ in the range of 21.69–47.60 μg/mL. Full article

(This article belongs to the Section Biological and Natural Products)

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12 pages, 4907 KiB

Open AccessArticle

Brazilian Plume (Justicia carnea L.) Leaf Wine-Colored Extract for Natural Dyeing of Mordant-Functionalized Cellulosic Fabric: Color Strength, Coordinates, and Fastness

by Jamiu Mosebolatan Jabar, Olugbenga Oludayo Oluwasina, Odunayo Michael Agunloye, Afolabi Clement Akinmoladun, Olamide Abigael Akande, Elizabeth Toyin Ojo and Hannah Olubukola Olojuolawe

Chemistry 2025, 7(1), 23; https://doi.org/10.3390/chemistry7010023 - 8 Feb 2025

Abstract

Increasing awareness of protecting the environment from chemically aided naive ecosystem degradation has encouraged the use of eco-friendly (biomass) materials in industrial production globally. This study investigated the application of a natural wine-colored extract from Brazilian plume (BP) leaf, obtained through a microwave-assisted [...] Read more.

Increasing awareness of protecting the environment from chemically aided naive ecosystem degradation has encouraged the use of eco-friendly (biomass) materials in industrial production globally. This study investigated the application of a natural wine-colored extract from Brazilian plume (BP) leaf, obtained through a microwave-assisted modern aqueous extraction technique, for toxic-free dyeing of mordant-functionalized cotton fabric. Dyeing of mordanted cotton fabric was optimized by varying dyeing parameters, such as dyeing contact time (10 to 90 min), pH (1 to 11), liquor ratio (1:5 to 1:30), and temperature (30 to 90 °C). UV-visible and Fourier transform infrared spectroscopic analyses confirmed that the chemical constituents of the extract were not altered by microwave radiation. The desired color strength (

K / S

) and dye-uptake (Q) were obtained at a dyeing time of 50 min, a pH of 7, a liquor ratio of 1:20, and a dyeing temperature of 60 °C. Varieties of elegant shades with desired colorfastness were developed through the involvement of less-toxic electrolyte and herbal mordants as functionalizing agents. BP extract is established as a potential sustainable and ecological colorant for textile industrial application. Full article

(This article belongs to the Section Green and Environmental Chemistry)

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13 pages, 14910 KiB

Open AccessArticle

Too Persistent to Resist: Aromaticity in 16e Osmapentalene Radicals Survives Regardless of Redox

by Shijie Pan, Jun Yan, Weitang Li, Zhigang Shuai and Jun Zhu

Chemistry 2025, 7(1), 22; https://doi.org/10.3390/chemistry7010022 - 8 Feb 2025

Abstract

As one of the most important concepts in organic chemistry, aromaticity has attracted considerable attention from both theoretical and experimental chemists. Limited by the traditional rules (Hückel’s rules and Baird’s rules), species can only achieve aromaticity in a single state (S₀ or [...] Read more.

As one of the most important concepts in organic chemistry, aromaticity has attracted considerable attention from both theoretical and experimental chemists. Limited by the traditional rules (Hückel’s rules and Baird’s rules), species can only achieve aromaticity in a single state (S₀ or T₁) in most cases. In 2018, our group first reported 16 electron osmapentalene that showed aromaticity in both the S₀ and T₁ states, which is defined as adaptive aromaticity. In recent years, although adaptive aromatic compounds have been expanded, the adaptive aromatics containing metal-centered radical has not been reported. Here, we carry out density functional theory calculations to explore the aromaticity of the corresponding radicals based on osmapentalyne and osmapentalenes in their S₀ states. It is found that the corresponding radicals of adaptive aromatic osmapentalene exhibit aromaticity regardless of the radicals formed by oxidation or reduction, supported by a series of aromaticity indices including ΔBL, NICS, AICD, EDDB, and ELF. In contrast, for the nonaromatic or antiaromatic compound in the T₁ state, only its cationic radical shows aromaticity. Furthermore, the spin density localization on the metal center is the key factor for the radicals to achieve aromaticity. Full article

(This article belongs to the Special Issue Open-Shell Systems—a Memorial Issue Dedicated to Professor Masayoshi Nakano)

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10 pages, 2021 KiB

Open AccessCommunication

Stable Fluorenyl Radicals Showing Tunable Doublet Emission

by Xudong Hou, Tingting Xu, Jun Zhu, Shaofei Wu and Jishan Wu

Chemistry 2025, 7(1), 21; https://doi.org/10.3390/chemistry7010021 - 7 Feb 2025

Abstract

Neutral organic radicals with intrinsic spin-allowed doublet emission have emerged as a promising class of luminescent materials, garnering significant research interest. However, the development of stable luminescent radicals with tunable emission remains challenging. Herein, we present the synthesis of a series of 9-(2,4,6-trichlorophenyl)-substituted [...] Read more.

Neutral organic radicals with intrinsic spin-allowed doublet emission have emerged as a promising class of luminescent materials, garnering significant research interest. However, the development of stable luminescent radicals with tunable emission remains challenging. Herein, we present the synthesis of a series of 9-(2,4,6-trichlorophenyl)-substituted fluorenyl radicals functionalized with various substituents at the 3,6-positions. These radicals exhibit enhanced stability through efficient spin delocalization and kinetic protection. Notably, they display red-shifted photoluminescence compared to traditional polychlorotriphenylmethyl radicals, with maximum emission wavelengths ranging from 679 nm to 744 nm. The mechanisms underlying the doublet emission, as well as their electrochemical properties, have been thoroughly investigated. Full article

(This article belongs to the Special Issue Open-Shell Systems—a Memorial Issue Dedicated to Professor Masayoshi Nakano)

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10 pages, 225 KiB

Open AccessArticle

Determination of Bioactive Compounds and Antioxidant Capacity in Leaf and Pulp of Annona muricata

by Mario Alberto Ruiz-López, Belinda Vargas-Guerrero, J. de Jesús Vargas-Radillo, Efigenia Montalvo-González, Eduardo Salcedo-Pérez, Ramon Rodriguez-Macias, Carmen Magdalena Gurrola-Diaz, Pedro Macedonio García-López and Juan Carlos Pizano-Andrade

Chemistry 2025, 7(1), 20; https://doi.org/10.3390/chemistry7010020 - 4 Feb 2025

Abstract

This study focused on analyzing and comparing bioactive compounds, specifically phenolics, in the pulp and leaf of Annona muricata (soursop), a crop highly valued in Latin America for its culinary and traditional uses. Methanolic extractions of leaf and pulp were performed for phytochemical [...] Read more.

This study focused on analyzing and comparing bioactive compounds, specifically phenolics, in the pulp and leaf of Annona muricata (soursop), a crop highly valued in Latin America for its culinary and traditional uses. Methanolic extractions of leaf and pulp were performed for phytochemical screening, high-performance liquid chromatography (HPLC), and measurements of antioxidant capacity. The results confirmed the presence of 15 phenolic compounds in the leaf and 14 in the pulp; these included phenolic acids and flavonoids. Shikimic acid was the main component identified, constituting 85 mg/g of the dry leaf sample and 17.50 mg/g of the dry pulp. The antioxidant capacity was determined using DPPH and FRAP. The percentages of inhibition were 70.93 and 15.10 in the leaf and pulp, respectively. This work expands our knowledge about the compounds present in A. muricata, which may be partly responsible for the known benefits of this plant for human health and nutrition. Full article

(This article belongs to the Section Biological and Natural Products)

8 pages, 1001 KiB

Open AccessArticle

Copper-Catalyzed Four-Component A³-Based Cascade Reaction: Facile Synthesis of 3-Oxetanone-Derived Spirocycles

by Rongkang Zhang, Liliang Huang, Aiguo Gu and Huangdi Feng

Chemistry 2025, 7(1), 19; https://doi.org/10.3390/chemistry7010019 - 4 Feb 2025

Abstract

3-Oxetanone-derived spirooxazolidines represent a class of building blocks for accessing diverse saturated heterocycles, but their synthetic methods remain unexplored. Herein, we demonstrate a highly atom-economic approach for the synthesis of diverse 3-oxetanone-derived N-propargyl spirooxazolidines via a CuBr₂/TFA co-catalyzed four-component A [...] Read more.

3-Oxetanone-derived spirooxazolidines represent a class of building blocks for accessing diverse saturated heterocycles, but their synthetic methods remain unexplored. Herein, we demonstrate a highly atom-economic approach for the synthesis of diverse 3-oxetanone-derived N-propargyl spirooxazolidines via a CuBr₂/TFA co-catalyzed four-component A³-based cascade reaction of a 1,2-amino alcohol, a 3-oxetanone, a formaldehyde, and an alkyne. This strategy is characterized by a wide substrate range and excellent chemoselectivity. In addition, the synthesized spirocycles could also be easily converted into other valuable compounds, facilitating potentially useful synthetic applications. Full article

(This article belongs to the Special Issue Oxygen-Containing Heterocyclic Compounds: Recent Advances in Chemistry)

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25 pages, 4457 KiB

Open AccessArticle

Pyrrolizine- and Indolizine-Derived Spirooxindoles: Synthesis, Antibacterial Activity and Inverse Docking Analysis

by Pablo Romo, María del Pilar Crespo, Mauricio Barreto, María Elena Burbano, Melissa Mejia-Gutierrez, Jairo Quiroga and Rodrigo Abonia

Chemistry 2025, 7(1), 18; https://doi.org/10.3390/chemistry7010018 - 1 Feb 2025

Abstract

Spirooxindoles are a family of heterocyclic compounds which bear the oxindole nucleus in their structures, which have a considerable pharmaceutical potential and which have been linked to various drugs for the treatment of diverse diseases. In this work, a wide variety of spirooxindoles [...] Read more.

Spirooxindoles are a family of heterocyclic compounds which bear the oxindole nucleus in their structures, which have a considerable pharmaceutical potential and which have been linked to various drugs for the treatment of diverse diseases. In this work, a wide variety of spirooxindoles bearing a pyrrolizinic nucleus were obtained by a 1,3-dipolar cycloaddition reaction between substituted isatins, trans-3-benzoyl acrylic acid and L-proline. In this approach, the target products 9a–m were obtained in 40–86% yields under heating to reflux in methanol over 2 h. Similarly, spirooxindoles containing an indolizinic nucleus 11a–j were obtained in 45–69% yields by switching L-proline for pipecolic acid under heating to reflux in acetonitrile for 8 h. The antibacterial activity of the obtained products was evaluated against P. aeruginosa, K. pneumoniae, E. coli, S. aureus, and N. gonorrhoeae, also including an inverse docking analysis. Results show that 9f and 11i, were the most active compounds against S. aureus, while compounds 9d and 9m displayed the higher activity against N. gonorrhoeae. Inverse docking analysis showed that compounds 9b, 11a 11e, and 11i displayed high affinity to the target protein 6TYM and 7Q6S, which are involved in biological pathways of diverse cancer and Parkinson diseases. Full article

(This article belongs to the Section Medicinal Chemistry)

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22 pages, 13794 KiB

Open AccessReview

Noble Metal-Based Catalysts for Selective Oxidation of HMF to FDCA: Progress in Reaction Mechanism and Active Sites

by Yingshuo Guo, Yitong Zhao, Shiao Gao, Binhong Lv and Zhijie Wu

Chemistry 2025, 7(1), 17; https://doi.org/10.3390/chemistry7010017 - 1 Feb 2025

Abstract

5-hydroxymethylfurfural (HMF) is oxidized to 2,5-furandicarboxylic acid (FDCA), which serves as a sustainable alternative to the petrochemical derivative terephthalic acid as a polyester monomer. Currently, noble metal catalysts that combine high HMF conversion rates with FDCA selectivity have become one of the mainstream [...] Read more.

5-hydroxymethylfurfural (HMF) is oxidized to 2,5-furandicarboxylic acid (FDCA), which serves as a sustainable alternative to the petrochemical derivative terephthalic acid as a polyester monomer. Currently, noble metal catalysts that combine high HMF conversion rates with FDCA selectivity have become one of the mainstream catalytic systems for HMF oxidation. This paper summarizes and discusses the research progress on HMF oxidation to FDCA over different noble metal-based catalysts by combining DFT theoretical calculations, introducing various reaction pathways and mechanisms of HMF oxidation. It also analyzes the characteristics and electronic properties of metal active sites, geometric effects, metal–support interactions, and confinement effects, discussing and revealing the roles and activation mechanisms of different metal active sites, the structure of catalysts, active substances, metal valence states, activity, and the relationship between metal and the oxidation of C=O and OH groups. Finally, it presents views on the challenges and future development in the design of noble metal-based catalysts. Full article

(This article belongs to the Special Issue Catalytic Conversion of Biomass and Its Derivatives)

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10 pages, 240 KiB

Open AccessReview

Nuclear Magnetic Resonance Gas-Phase Studies of Spin-Spin Couplings in Molecules

by Karol Jackowski

Chemistry 2025, 7(1), 16; https://doi.org/10.3390/chemistry7010016 - 26 Jan 2025

Abstract

This paper overviews gas phase experiments with respect to one fundamental part of nuclear magnetic resonance (NMR) spectra. Indirect spin-spin coupling is an important parameter of NMR spectra and is observed as the splitting of spectral signals. A molecule containing two different magnetic [...] Read more.

This paper overviews gas phase experiments with respect to one fundamental part of nuclear magnetic resonance (NMR) spectra. Indirect spin-spin coupling is an important parameter of NMR spectra and is observed as the splitting of spectral signals. A molecule containing two different magnetic nuclei (e.g., hydrogen HD, HT, or DT) exhibits this interaction in an external magnetic field measured as the spin-spin coupling parameter, ⁿJ(NN′). Modern quantum chemical methods allow the precise calculation of spin-spin coupling, but it is never easy because ⁿJ(NN′) is modified by temperature and intermolecular interactions. Accurate calculations can be performed only for small isolated molecules. NMR spectroscopy can deliver measurements of spin-spin couplings for isolated molecules if ⁿJ(NN′) parameters are observed in the gas phase as a function of density. The extrapolation of such measurements to the zero-density limit permits ⁿJ₀(NN′) determination free from intermolecular interactions. The latter technique can also be applied to liquid vapors in molecules like acetonitrile or water. Spin-spin couplings across one chemical bond (¹J₀(NN′)) are the largest and most important for theoretical modeling. The present review reports numerous ¹J₀(NN′) parameters recently measured by multinuclear NMR spectra of gaseous samples. Full article

(This article belongs to the Section Physical Chemistry and Chemical Physics)

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13 pages, 4484 KiB

Open AccessArticle

Synthesis and Characterization of Quinoxaline-Fused Cyclopenta[cd]azulene

by Tomohiro Oda, Yuina Onishi, Akihito Konishi and Makoto Yasuda

Chemistry 2025, 7(1), 15; https://doi.org/10.3390/chemistry7010015 - 23 Jan 2025

Abstract

Azulene-based polycyclic hydrocarbons have garnered much attention as potential materials for organic optoelectronic devices and as molecular models for graphene nanosheets with structural defects. Although various methods for ring fusions to an azulene core have been established for ring fusions to an azulene [...] Read more.

Azulene-based polycyclic hydrocarbons have garnered much attention as potential materials for organic optoelectronic devices and as molecular models for graphene nanosheets with structural defects. Although various methods for ring fusions to an azulene core have been established for ring fusions to an azulene core, efficient synthetic methodologies for ortho- and peri-fusion to an azulene core are still lacking, which hinders the investigation of the effect of the ortho- and peri-fusion on the electronic properties of the embedded azulene core. Herein, we describe the synthesis and characterization of quinoxaline-fused cyclopenta[cd]azulene 4 as a new ortho- and peri-fused azulene derivative. The target molecule 4 was successfully synthesized in four steps from 4-methylazulene. The ring annulation decreased the lowest excitation energy compared with that of azulene and its structural isomer 5 and led to multiple reversible reduction processes. Characterization of the molecular geometry and optoelectronic properties of 4 revealed that the embedded azulene core preserves its original aromaticity, while the fused quinoxaline acts as a nucleophilic and basic site. These features suggest that 4 could serve as a metal ligand, a near-infrared absorber, and a component in organic functional devices. Full article

(This article belongs to the Special Issue Open-Shell Systems—a Memorial Issue Dedicated to Professor Masayoshi Nakano)

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