-
Journal of Molecular Graphics &... Jun 2020Rapid electrocyclization is proposed under radical anionic conditions in organic photochromes. DFT calculations have been performed to investigate the radical anion...
Rapid electrocyclization is proposed under radical anionic conditions in organic photochromes. DFT calculations have been performed to investigate the radical anion mediated electrocyclization in different organic photochromes. Furthermore, the activation barriers under radical anionic conditions are compared with those in neutral and radical cationic conditions. The nuclear independent chemical shift (NICS(0)) and synchronicity calculations have been performed for the confirmation of concerted nature and aromatic character of transition states, respectively. The activation barrier for thermal return of cyclophanediene (CPD) to dihydropyrene (DHP) under radical anionic conditions is very lower (ΔH = 5.92 kcal/mol, ΔG = 6.97 kcal/mol) than under neutral conditions, but higher than that in radical cationic conditions (ΔH = 3.13 kcal/mol, ΔG = 4.0 kcal/mol). Similarly, the other prominent classes of photochromes; dithienylethene (ΔH = 20.12 kcal/mol, ΔG = 21.55 kcal/mol) and vinylheptafulvene (ΔH = 23.72 kcal/mol, ΔG = 24.82 kcal/mol) have shown decreased activation barrier under radical anionic condition. However, activation barrier of fulgide under radical anionic conditions is not different than those under neutral and radical cationic conditions. Synchronicity and NICS(0) values for organic photochromes also show significant changes under radical anionic conditions.
Topics: Anions; Thermodynamics
PubMed: 32023507
DOI: 10.1016/j.jmgm.2020.107550 -
The Journal of Physical Chemistry. B Sep 2007Changes in optical rotation of some alpha-amino acids are induced by electrolytes. Such effects on l- and d-enantiomers of a range of amino acids are explored for sodium...
Changes in optical rotation of some alpha-amino acids are induced by electrolytes. Such effects on l- and d-enantiomers of a range of amino acids are explored for sodium salts with varying anion. The amino acids studied were alanine, aspartic acid, glutamic acid, glutamine, proline, threonine, and tryptophan. The anion's polarizability in solution accounts for the change in [alpha] only for the halides. Self-association of amino acids in solution and pH changes due to the presence of the electrolytes do not account for the observed variations in optical activity. Specific interactions of anions with the chiral amino acids (Hofmeister effects) and salt-induced perturbations of the amino acid hydration shell appear to be responsible for the effects, and conformational changes in the chiral solutes due to the presence of ionic species are discussed.
Topics: Amino Acids; Anions; Computer Simulation; Dipeptides; Hydrogen Bonding; Hydrogen-Ion Concentration; Models, Molecular; Optics and Photonics; Stereoisomerism; Thermodynamics; Threonine
PubMed: 17691834
DOI: 10.1021/jp0721806 -
Chemistry (Weinheim An Der Bergstrasse,... Jul 2011Two series of C3-benzamido and O2-anion-substituted galactopyranosides were synthesized and studied as binders to arginine-rich proteins galectin-1, -3, -7, -8N...
Two series of C3-benzamido and O2-anion-substituted galactopyranosides were synthesized and studied as binders to arginine-rich proteins galectin-1, -3, -7, -8N (N-terminal domain), and -9N (N-terminal domain). The first series had a 4-methylbenzamide at C3 and the anionic O2-substituent was varied. The second series varied the 4-substituent of the C3-benzamide, whereas the anionic O2 substituent was kept as a sulfate. The influence of the O2-anion substituent correlated negatively with the oxygen charge density in case of galectin-1, -3, and -9N. In the second series, the electron-donating capacity of the 4-substituent of the C3-benzamides correlated positively with the magnitude of the affinity enhancement by the 2O-sulfate.
Topics: Animals; Anions; Arginine; Benzamides; Galactose; Galectins; Models, Molecular; Protein Binding; Protein Structure, Tertiary; Structure-Activity Relationship
PubMed: 21656580
DOI: 10.1002/chem.201003247 -
Analytical and Bioanalytical Chemistry Aug 2008An anion exchange monolithic silica capillary column was prepared by surface modification of a hybrid monolithic silica capillary column prepared from a mixture of...
An anion exchange monolithic silica capillary column was prepared by surface modification of a hybrid monolithic silica capillary column prepared from a mixture of tetramethoxysilane (TMOS) and methyltrimethoxysilane (MTMS). The surface modification was carried out by on-column copolymerization of N-[3-(dimethylamino)propyl]acrylamide methyl chloride-quaternary salt (DMAPAA-Q) with 3-methacryloxypropyl moieties bonded as an anchor to the silica surface to form a strong anion exchange stationary phase. The columns were examined for their performance in liquid chromatography (LC) and capillary electrochromatography (CEC) separations of common anions. The ions were separated using 50 mM phosphate buffer at pH 6.6. Evaluation by LC produced an average of 30,000 theoretical plates (33 cm column length) for the inorganic anions and nucleotides. Evaluation by CEC, using the same buffer, produced enhanced chromatographic performance of up to ca. 90,000 theoretical plates and a theoretical plate height of ca. 4 mum. Although reduced efficiency was observed for inorganic anions that were retained a long time, the results of this study highlight the potential utility of the DMAPAA-Q stationary phase for anion separations.
Topics: Acrylamides; Anions; Bromates; Chromatography, Gel; Iodates; Iodides; Methyl Chloride; Silanes; Silicon Dioxide; Thiocyanates; Thiourea
PubMed: 18458888
DOI: 10.1007/s00216-008-2063-3 -
Chemical Communications (Cambridge,... Jan 2008Sulfonamide groups, commonly used as neutral hydrogen bond donors in a wide variety of anion receptors, deprotonate upon addition of certain basic anionic guests in two...
Sulfonamide groups, commonly used as neutral hydrogen bond donors in a wide variety of anion receptors, deprotonate upon addition of certain basic anionic guests in two simple functionalised ureas.
Topics: Anions; Crystallography, X-Ray; Models, Molecular; Molecular Structure; Protons; Sulfonamides; Urea
PubMed: 18401892
DOI: 10.1039/b713431b -
Nature Chemistry Sep 2012Biochemical systems are adaptable, capable of reconstitution at all levels to achieve the functions associated with life. Synthetic chemical systems are more limited in...
Biochemical systems are adaptable, capable of reconstitution at all levels to achieve the functions associated with life. Synthetic chemical systems are more limited in their ability to reorganize to achieve new functions; they can reconfigure to bind an added substrate (template effect) or one binding event may modulate a receptor's affinity for a second substrate (allosteric effect). Here we describe a synthetic chemical system that is capable of structural reconstitution on receipt of one anionic signal (perchlorate) to create a tight binding pocket for another anion (chloride). The complex, barrel-like structure of the chloride receptor is templated by five perchlorate anions. This second-order templation phenomenon allows chemical networks to be envisaged that express more complex responses to chemical signals than is currently feasible.
Topics: Anions; Chlorides; Cobalt; Combinatorial Chemistry Techniques; Coordination Complexes; Lithium Compounds; Models, Molecular; Molecular Conformation; Perchlorates; Pyridines; Toluidines
PubMed: 22914197
DOI: 10.1038/nchem.1407 -
Current Opinion in Drug Discovery &... Nov 2007Umpolung catalysis involving carbonyls is a long-established concept in organic synthesis, but is arguably underdeveloped relative to other modes of catalysis. Acyl... (Review)
Review
Umpolung catalysis involving carbonyls is a long-established concept in organic synthesis, but is arguably underdeveloped relative to other modes of catalysis. Acyl anion and homoenolate catalysis provides unique and rapid access to functional group arrays that may otherwise be challenging to synthesize directly. Catalysis is only feasible when a strict set of requirements is met, and to date only a small number of molecules are known to meet these criteria. This review highlights innovative advances that have been made in this field within the past four years and includes research aimed toward catalyst development, new reaction discovery and stereocontrol.
Topics: Acylation; Anions; Catalysis; Chemistry, Organic; Drug Design; Molecular Structure; Organic Chemicals
PubMed: 17987521
DOI: No ID Found -
Organic & Biomolecular Chemistry Oct 2015In this study, we report a gas-phase benzyl anion transfer via intramolecular aromatic nucleophilic substitution (SNAr) during the course of tandem mass spectrometry of...
In this study, we report a gas-phase benzyl anion transfer via intramolecular aromatic nucleophilic substitution (SNAr) during the course of tandem mass spectrometry of deprotonated N-(phenylsulfonyl)-benzeneacetamide. Upon collisional activation, the formation of the initial ion/neutral complex ([C6H5CH2(-)/C6H5SO2NCO]), which was generated by heterolytic cleavage of the CH2-CO bond, is proposed as the key step. Subsequently, the anionic counterpart, benzyl anion, is transferred to conduct the intra-complex SNAr reaction. After losing neutral HNCO, the intermediate gives rise to product ion B at m/z 231, whose structure is confirmed by comparing the multistage spectra with those of deprotonated 2-benzylbenzenesulfinic acid and (benzylsulfonyl)benzene. In addition, intra-complex proton transfer is also observed within the complex [C6H5CH2(-)/C6H5SO2NCO] to generate product ion C at m/z 182. The INC-mediated mechanism was corroborated by theoretical calculations, isotope experiments, breakdown curve, substituent experiments, etc. This work may provide further understanding of the physicochemical properties of the gaseous benzyl anion.
Topics: Acetamides; Anions; Benzyl Compounds; Molecular Structure; Protons; Quantum Theory; Sulfhydryl Compounds
PubMed: 26309220
DOI: 10.1039/c5ob01582k -
Angewandte Chemie (International Ed. in... Jun 2023Mixed-anion compounds widen the chemical space of attainable materials compared to single anionic compounds, but the exploration of their structural diversity is limited...
Mixed-anion compounds widen the chemical space of attainable materials compared to single anionic compounds, but the exploration of their structural diversity is limited by common synthetic paths. Especially, oxychlorides rely mainly on layered structures, which suffer from low stability during photo(electro)catalytic processes. Herein we report a strategy to design a new polar 3D tetrahedral framework with composition Zn Si O Cl . We use a molten salt medium to enable low temperature crystallization of nanowires of this new compound, by relying on tetrahedral building units present in the melt to build the connectivity of the oxychloride. These units are combined with silicon-based connectors from a non-oxidic Zintl phase to enable precise tuning of the oxygen content. This structure brings high chemical and thermal stability, as well as strongly anisotropic hole mobility along the polar axis. These features, associated with the ability to adjust the transport properties by doping, enable to tune water splitting properties for photoelectrocatalytic H evolution and water oxidation. This work then paves the way to a new family of mixed-anion solids.
Topics: Sodium Chloride; Anions; Nanostructures; Zinc; Silicon Dioxide; Chlorides; Catalysis; Electrochemistry
PubMed: 37042950
DOI: 10.1002/anie.202303487 -
Journal of Receptor and Signal... 2009A series of artificial 2,2'-bipyridine receptors (1, 2, 3) containing phenol group have been designed and synthesized. Their anion-binding properties are evaluated for...
A series of artificial 2,2'-bipyridine receptors (1, 2, 3) containing phenol group have been designed and synthesized. Their anion-binding properties are evaluated for various anions (F(-), Cl(-), Br(-), I(-), AcO(-) and H(2)PO(4)(-)) by UV-vis titration experiment in order to research the impact of different substituents on anion-recognition properties. Results indicate that the anion binding abilities can be tuned by electron push-pull properties of substituents on the phenyl ortho- or para-position of the receptors. In addition, receptor 1 is sensitive for F(-) detection without the interference of other studied anions, and receptors 2 and 3 are sensitive for H(2)PO(4)(-) detection.
Topics: 2,2'-Dipyridyl; Anions; Hydroxides; Magnetic Resonance Spectroscopy; Molecular Structure; Oxidation-Reduction; Phenols; Spectrophotometry, Ultraviolet
PubMed: 19604128
DOI: 10.1080/10799890903078481