Chemistry

10 pages, 1372 KiB

Open AccessFeature PaperArticle

Appropriate Buffers for Studying the Bioinorganic Chemistry of Silver(I)

by Lucille Babel, Soledad Bonnet-Gómez and Katharina M. Fromm

Chemistry 2020, 2(1), 193-202; https://doi.org/10.3390/chemistry2010012 - 22 Mar 2020

Cited by 10 | Viewed by 5335

Silver(I) is being largely studied for its antimicrobial properties. In parallel to that growing interest, some researchers are investigating the effect of this ion on eukaryotes and the mechanism of silver resistance of certain bacteria. For these studies, and more generally in biology, [...] Read more.

Silver(I) is being largely studied for its antimicrobial properties. In parallel to that growing interest, some researchers are investigating the effect of this ion on eukaryotes and the mechanism of silver resistance of certain bacteria. For these studies, and more generally in biology, it is necessary to work in buffer systems that are most suitable, i.e., that interact least with silver cations. Selected buffers such as 4-(2-hydroxyethyl)-1-piperazineethane sulfonic acid (HEPES) were therefore investigated for their use in the presence of silver nitrate. Potentiometric titrations allowed to determine stability constants for the formation of (Ag(Buffer)) complexes. The obtained values were adapted to extract the apparent binding constants at physiological pH. The percentage of metal ions bound to the buffer was calculated at this pH for given concentrations of buffer and silver to realize at which extent silver was interacting with the buffer. We found that in the micromolar range, HEPES buffer is sufficiently coordinating to silver to have a non-negligible effect on the thermodynamic parameters determined for an analyte. Morpholinic buffers were more suitable as they turned out to be weaker complexing agents. We thus recommend the use of MOPS for studies of physiological pH. Full article

(This article belongs to the Special Issue Radically Different—A Themed Issue in Honor of Professor Bernd Giese on the Occasion of His 80th Birthday)

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14 pages, 4199 KiB

Open AccessArticle

From Frustrated Packing to Tecton-Driven Porous Molecular Solids

by Chamara A. Gunawardana, Abhijeet S. Sinha, Eric W. Reinheimer and Christer B. Aakeröy

Chemistry 2020, 2(1), 179-192; https://doi.org/10.3390/chemistry2010011 - 13 Mar 2020

Cited by 8 | Viewed by 4630

Abstract

Structurally divergent molecules containing bulky substituents tend to produce porous materials via frustrated packing. Two rigid tetrahedral cores, tetraphenylmethane and 1,3,5,7-tetraphenyladamantane, grafted peripherally with four (trimethylsilyl)ethynyl moieties, were found to have only isolated voids in their crystal structures. Hence, they were modified into [...] Read more.

Structurally divergent molecules containing bulky substituents tend to produce porous materials via frustrated packing. Two rigid tetrahedral cores, tetraphenylmethane and 1,3,5,7-tetraphenyladamantane, grafted peripherally with four (trimethylsilyl)ethynyl moieties, were found to have only isolated voids in their crystal structures. Hence, they were modified into tecton-like entities, tetrakis(4-(iodoethynyl)phenyl)methane [I₄TEPM] and 1,3,5,7-tetrakis(4-(iodoethynyl)phenyl)adamantane [I₄TEPA], in order to deliberately use the motif-forming characteristics of iodoethynyl units to enhance crystal porosity. I₄TEPM not only holds increased free volume compared to its precursor, but also forms one-dimensional channels. Furthermore, it readily co-crystallizes with Lewis basic solvents to afford two-component porous crystals. Full article

(This article belongs to the Special Issue Supramolecular Chemistry in the 3rd Millennium)

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78 pages, 26069 KiB

Open AccessFeature PaperReview

Hydrogen Peroxide as a Green Oxidant for the Selective Catalytic Oxidation of Benzylic and Heterocyclic Alcohols in Different Media: An Overview

by Majid M. Heravi, Nastaran Ghalavand and Elaheh Hashemi

Chemistry 2020, 2(1), 101-178; https://doi.org/10.3390/chemistry2010010 - 5 Mar 2020

Cited by 21 | Viewed by 8108

Abstract

Among a plethora of known and established oxidant in organic chemistry, hydrogen peroxide stands in a special position. It is commercially and inexpensively available, highly effective, selective, and more importantly it is compatible with current environmental concerns, dictated by principles of green chemistry. [...] Read more.

Among a plethora of known and established oxidant in organic chemistry, hydrogen peroxide stands in a special position. It is commercially and inexpensively available, highly effective, selective, and more importantly it is compatible with current environmental concerns, dictated by principles of green chemistry. Several chemicals or their intermediates that are important in our daily life such as pharmaceuticals, flavors, fragrances, etc. are products of oxidation of alcohols. In this review, we introduce hydrogen peroxide as an effective, selective, green and privileged oxidant for the catalyzed oxidation of primary and secondary benzylic and heterocyclic alcohols to corresponding carbonyl compounds in different media such as aqueous media, under solvent-free conditions, various organic solvent, and dual-phase system. Full article

(This article belongs to the Section Catalysis)

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8 pages, 1477 KiB

Open AccessArticle

Controlled Stepwise Synthesis and Characterization of a Ternary Multicomponent Crystal with 2-Methylresorcinol

by Daniel Komisarek, Carsten Schauerte and Klaus Merz

Chemistry 2020, 2(1), 93-100; https://doi.org/10.3390/chemistry2010009 - 4 Mar 2020

Cited by 3 | Viewed by 2939

Abstract

A typical approach of a multicomponent crystal design starts with a retrosynthetic analysis of the target molecule followed by a one-pot reaction of all components. To develop protocols for multicomponent crystal syntheses, controlled stepwise syntheses of a selected crystalline ternary multicomponent system 1 [...] Read more.

A typical approach of a multicomponent crystal design starts with a retrosynthetic analysis of the target molecule followed by a one-pot reaction of all components. To develop protocols for multicomponent crystal syntheses, controlled stepwise syntheses of a selected crystalline ternary multicomponent system 1 involving 2-methylresorcinol (MRS), tetramethyl-pyrazine (TMP), and 1,2-bis(4-pyridyl)ethane (BPE) are presented. The obtained binary cocrystals 2 (involving MRS and TMP) and 3 (involving MRS and BPE) as well as the final resulting ternary multicomponent system 1 were characterized by X-ray analysis. Full article

(This article belongs to the Special Issue Supramolecular Chemistry in the 3rd Millennium)

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13 pages, 3157 KiB

Open AccessFeature PaperReview

Addition of Heteroatom Radicals to endo-Glycals †

by Torsten Linker

Chemistry 2020, 2(1), 80-92; https://doi.org/10.3390/chemistry2010008 - 20 Feb 2020

Cited by 9 | Viewed by 4060

Abstract

Radical reactions have found many applications in carbohydrate chemistry, especially in the construction of carbon–carbon bonds. The formation of carbon–heteroatom bonds has been less intensively studied. This mini-review will summarize the efforts to add heteroatom radicals to unsaturated carbohydrates like endo-glycals. Starting [...] Read more.

Radical reactions have found many applications in carbohydrate chemistry, especially in the construction of carbon–carbon bonds. The formation of carbon–heteroatom bonds has been less intensively studied. This mini-review will summarize the efforts to add heteroatom radicals to unsaturated carbohydrates like endo-glycals. Starting from early examples, developed more than 50 years ago, the importance of such reactions for carbohydrate chemistry and recent applications will be discussed. After a short introduction, the mini-review is divided in sub-chapters according to the heteroatoms halogen, nitrogen, phosphorus, and sulfur. The mechanisms of radical generation by chemical or photochemical processes and the subsequent reactions of the radicals at the 1-position will be discussed. This mini-review cannot cover all aspects of heteroatom-centered radicals in carbohydrate chemistry, but should provide an overview of the various strategies and future perspectives. Full article

(This article belongs to the Special Issue Radically Different—A Themed Issue in Honor of Professor Bernd Giese on the Occasion of His 80th Birthday)

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17 pages, 4351 KiB

Open AccessFeature PaperReview

Uranyl Ion Complexes of Polycarboxylates: Steps towards Isolated Photoactive Cavities

by Jack Harrowfield and Pierre Thuéry

Chemistry 2020, 2(1), 63-79; https://doi.org/10.3390/chemistry2010007 - 20 Feb 2020

Cited by 12 | Viewed by 3097

Abstract

Consideration of the extensive family of known uranyl ion complexes of polycarboxylate ligands shows that there are quite numerous examples of crystalline solids containing capsular, closed oligomeric species with the potential for use as selective heterogeneous photo-oxidation catalysts. None of them have yet [...] Read more.

Consideration of the extensive family of known uranyl ion complexes of polycarboxylate ligands shows that there are quite numerous examples of crystalline solids containing capsular, closed oligomeric species with the potential for use as selective heterogeneous photo-oxidation catalysts. None of them have yet been assessed for this purpose, and some have obvious deficiencies, although related framework species have been shown to have the necessary luminescence, porosity and, to some degree, selectivity. Aspects of ligand design and complex composition necessary for the synthesis of uranyl ion cages with appropriate luminescence and chemical properties for use in selective photo-oxidation catalysis have been analysed in relation to the characteristics of known capsules. Full article

(This article belongs to the Special Issue Supramolecular Chemistry in the 3rd Millennium)

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12 pages, 5068 KiB

Open AccessFeature PaperArticle

_∞³[Cu₂(mand)₂(hmt)]–MOF: A Synergetic Effect between Cu(II) and Hexamethylenetetramine in the Henry Reaction

by Horațiu Szalad, Natalia Candu, Bogdan Cojocaru, Traian D. Păsătoiu, Marius Andruh and Vasile I. Pârvulescu

Chemistry 2020, 2(1), 50-62; https://doi.org/10.3390/chemistry2010006 - 13 Feb 2020

Cited by 6 | Viewed by 3338

Abstract

_∞³[Cu₂(mand)₂(hmt)]·H₂O (where mand is totally deprotonated mandelic acid (racemic mixture) and hmt is hexamethylenetetramine) proved to be a stable metal–organic framework (MOF) structure under thermal activation and catalytic conditions, as confirmed by both the in [...] Read more.

_∞³[Cu₂(mand)₂(hmt)]·H₂O (where mand is totally deprotonated mandelic acid (racemic mixture) and hmt is hexamethylenetetramine) proved to be a stable metal–organic framework (MOF) structure under thermal activation and catalytic conditions, as confirmed by both the in situ PXRD (Powder X-ray diffraction) and ATR–FTIR (Attenuated total reflection-Fourier-transform infrared spectroscopy) haracterization. The non-activated MOF was completely inert as catalyst for the Henry reaction, as the accessibility of the substrates to the channels was completely blocked by H-bonded water to the mand entities and CO₂ adsorbed on the Lewis basic sites of the hmt. Heating at 140 °C removed these molecules. Only an insignificant change in the relative ratios of the XRD facets due to the capillary forces associated to the removal of the guest molecules from the network has been observed. This treatment afforded the accessibility of nitromethane and various aldehydes (4-bromobenzaldehyde, 4-nitrobenzaldehyde, and p-tolualdehyde) to the active catalytic sites, leading to conversions up to 48% and selectivities up to 98% for the desired nitroaldol products. The behavior of the catalyst is solvent-sensitive. Protic solvents completely inhibited the reaction due to the above-mentioned strong H-bonds. Accordingly, very good results were obtained only with aprotic solvents such as acetonitrile and 1,4-dioxane. The synthesized MOF is completely recyclable as demonstrated for five successive cycles. Full article

(This article belongs to the Special Issue 2020 Profile Papers by Chemistry' Editorial Board Members)

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17 pages, 7672 KiB

Open AccessFeature PaperArticle

Metallosupramolecular Compounds Based on Copper(II/I) Chloride and Two Bis-Tetrazole Organosulfur Ligands

by Olaya Gómez-Paz, Rosa Carballo, Ana Belén Lago and Ezequiel M. Vázquez-López

Chemistry 2020, 2(1), 33-49; https://doi.org/10.3390/chemistry2010005 - 4 Feb 2020

Cited by 4 | Viewed by 3295

Abstract

The present work assesses the ability of two flexible bis-tetrazole organosulfur ligands to build up different metallosupramolecular compounds based on the analysis of the different supramolecular interactions. The reaction of copper(II) chloride dihydrate with the N,N’-donor dithioether ligands bis(1-methyl-1H [...] Read more.

The present work assesses the ability of two flexible bis-tetrazole organosulfur ligands to build up different metallosupramolecular compounds based on the analysis of the different supramolecular interactions. The reaction of copper(II) chloride dihydrate with the N,N’-donor dithioether ligands bis(1-methyl-1H-tetrazole-5-ylthio)methane (BMTTM) and 1,2-bis(1-methyl-1H-tetrazole-5-ylthio)ethane (BMTTE) was investigated using different synthetic methods. Four compounds have been obtained as single crystals: two pseudopolymorphic 1D Cu(II) coordination polymers with the ligand BMTTM, a 2D Cu(II) coordination polymer and a discrete Cu(I) tetramer with the BMTTE ligand. The effects of the weak interactions on the crystal packing and the Hirshfeld surfaces of the structures were analyzed to clarify the nature of the intermolecular interactions. Full article

(This article belongs to the Special Issue Supramolecular Chemistry in the 3rd Millennium)

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11 pages, 2628 KiB

Open AccessFeature PaperArticle

Catalysis of an Aldol Condensation Using a Coordination Cage

by Cristina Mozaceanu, Christopher G. P. Taylor, Jerico R. Piper, Stephen P. Argent and Michael D. Ward

Chemistry 2020, 2(1), 22-32; https://doi.org/10.3390/chemistry2010004 - 25 Jan 2020

Cited by 15 | Viewed by 4599

Abstract

The aldol condensation of indane-1,3-dione (ID) to give ‘bindone’ in water is catalysed by an M₈L₁₂ cubic coordination cage (H^w). The absolute rate of reaction is slow under weakly acidic conditions (pH 3–4), but in [...] Read more.

The aldol condensation of indane-1,3-dione (ID) to give ‘bindone’ in water is catalysed by an M₈L₁₂ cubic coordination cage (H^w). The absolute rate of reaction is slow under weakly acidic conditions (pH 3–4), but in the absence of a catalyst it is undetectable. In water, the binding constant of ID in the cavity of H^w is ca. 2.4 (±1.2) × 10³ M⁻¹, giving a ∆G for the binding of −19.3 (±1.2) kJ mol⁻¹. The crystal structure of the complex revealed the presence of two molecules of the guest ID stacked inside the cavity, giving a packing coefficient of 74% as well as another molecule hydrogen-bonded to the cage’s exterior surface. We suggest that the catalysis occurs due to the stabilisation of the enolate anion of ID by the 16+ surface of the cage, which also attracts molecules of neutral ID to the surface because of its hydrophobicity. The cage, therefore, brings together neutral ID and its enolate anion via two different interactions to catalyse the reaction, which—as the control experiments show—occurs at the exterior surface of the cage and not inside the cage cavity. Full article

(This article belongs to the Special Issue Supramolecular Chemistry in the 3rd Millennium)

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11 pages, 1766 KiB

Open AccessArticle

Selective Proton-Mediated Transport by Electrogenic K⁺-Binding Macrocycles

by Yu-Hao Li, Shao-Ping Zheng, Dawei Wang and Mihail Barboiu

Chemistry 2020, 2(1), 11-21; https://doi.org/10.3390/chemistry2010003 - 20 Jan 2020

Cited by 3 | Viewed by 2769

Abstract

Synthetic K⁺-binding macrocycles have potential as therapeutic agents for diseases associated with KcsA K⁺ channel dysfunction. We recently discovered that artificial self-assembled n-alkyl-benzoureido-15-crown-5-ether form selective ion-channels for K⁺ cations, which are highly preferred to Na⁺ cations. Here, [...] Read more.

Synthetic K⁺-binding macrocycles have potential as therapeutic agents for diseases associated with KcsA K⁺ channel dysfunction. We recently discovered that artificial self-assembled n-alkyl-benzoureido-15-crown-5-ether form selective ion-channels for K⁺ cations, which are highly preferred to Na⁺ cations. Here, we describe an impressive selective activation of the K⁺ transport via electrogenic macrocycles, stimulated by the addition of the carbonyl cyanide-4-(trifluoromethoxy) phenylhydrazone (FCCP) proton carrier. The transport performances show that both the position of branching or the size of appended alkyl arms favor high transport activity and selectivity S_K⁺_/Na⁺ up to 48.8, one of the best values reported up to now. Our study demonstrates that high K⁺/Na⁺ selectivity obtained with natural KcsA K⁺ channels is achievable using simpler artificial macrocycles displaying constitutional functions. Full article

(This article belongs to the Special Issue Supramolecular Chemistry in the 3rd Millennium)

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9 pages, 3895 KiB

Open AccessArticle

Preparation of Activated Carbon from Coffee Waste as an Adsorbent for the Removal of Chromium (III) from Water. Optimization for an Experimental Box-Behnken Design

by Adolfo Eduardo Obaya Valdivia, Carlos Montaño Osorio and Yolanda Marina Vargas Rodríguez

Chemistry 2020, 2(1), 2-10; https://doi.org/10.3390/chemistry2010002 - 19 Jan 2020

Cited by 8 | Viewed by 4522

Abstract

Coffee grounds are an organic waste consisting of the ground, roasted and processed grain for the extraction of coffee, being of great volume the waste obtained, which, if not treated and preserved for a long time, emanates unpleasant aromas and becomes an optimal [...] Read more.

Coffee grounds are an organic waste consisting of the ground, roasted and processed grain for the extraction of coffee, being of great volume the waste obtained, which, if not treated and preserved for a long time, emanates unpleasant aromas and becomes an optimal means for the proliferation of flies, and other pests. Activated carbon has the characteristic of being a material that has a large surface area; because of this, it is used in adsorption, which refers to the retention of atoms, ions, and molecules on its surface. In this paper, the production of activated carbon is presented by means of the physicochemical activation of coffee waste by calcining at 900 °C and subsequent activation with sulfuric acid, as well as the Box–Behnken design of three factors for chromium (III) adsorption optimization. It is determined that the optimal conditions for performing the adsorption are pH = 3 and a contact time of 140 min. According to the analysis of variance for the experimental design, it is determined that the initial chromium formation is not significant for the adsorption process. Under the optimal adsorb conditions of 96%, an application is given to the erasure of coffee for the production of activated carbon, which serves as the adsorbent agent applied to the removal of chromium (III) aqueous. The area of activated carbon obtained is 13657.89 ± 251.09 m²/g determined by the acetic acid adsorption isotherm method. Full article

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

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1 pages, 162 KiB

Open AccessEditorial

Acknowledgement to Reviewers of Chemistry in 2019

by Chemistry Editorial Office

Chemistry 2020, 2(1), 1; https://doi.org/10.3390/chemistry2010001 - 16 Jan 2020

Cited by 1 | Viewed by 1770

Abstract

The editorial team greatly appreciates the reviewers who have dedicated their considerable time and expertise to the journal’s rigorous editorial process over the past 12 months, regardless of whether the papers are finally published or not [...] Full article

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Chemistry, Volume 2, Issue 1 (March 2020) – 12 articles

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