Thiol Reduction of Arsenite and Selenite: DFT Modeling of the Pathways to an As–Se Bond

The reactivity of arsenite and selenite with biological thiols plays an important role in the toxicity of these elements. However, toxic effects are eliminated when the species are coadministered, due to the antagonistic relationship between selenium and arsenic. The reduction of arsenous acid and selenious acid by thiol and the formation of an As–Se species have been modeled using density functional theory (DFT) and solvent-assisted proton exchange (SAPE), a microsolvation technique that uses a network of water molecules to mimic the participation of bulk solvent in proton transfer processes. Activation barriers and relative energies were calculated for the stepwise thiol reduction of arsenite to form As­(SR)₃ and selenious acid to first form a selenotrisulfide (Se­(SR)₂) and then H₂Se. Several pathways were explored for the formation of an As–Se bond: the nucleophilic attack of selenide or selenopersulfide on As­(OH)₃, (RS)­As­(OH)₂, and (RS)₂AsOH to form (RS)₂AsSeH. On the basis of the lower activation barrier and bioavailability of (RS)₂AsOH, the reaction of H₂Se with (RS)₂AsOH is deemed the most favorable, consistent with previous experimental studies

Ruthenium(II) Dichloride Complexes of Chiral, Tetradentate Aminosulfoxide Ligands: Stereoisomerism and Redox-Induced Linkage Isomerism

Ruthenium­(II) dichloride complexes of two chiral tetradentate aminosulfoxide ligands, varying only in the N–N linker, were synthesized. With each ligand, two major isomers formed, and these were structurally assigned and characterized through a combination of NMR and UV–vis spectroscopies, X-ray crystallography, and density functional theory calculations. The <i>cis</i>-β geometric isomer was formed by each ligand, whereas the <i>trans</i> and <i>cis</i>-α geometric isomers were significant components for one ligand only. Cyclic voltammetry studies show that only the <i>cis</i>-β isomers undergo linkage isomerism upon oxidation to ruthenium­(III), whereas the <i>trans</i> and <i>cis</i>-α isomers show simple reversible redox couples

Ruthenium(II) Dichloride Complexes of Chiral, Tetradentate Aminosulfoxide Ligands: Stereoisomerism and Redox-Induced Linkage Isomerism

Ruthenium­(II) dichloride complexes of two chiral tetradentate aminosulfoxide ligands, varying only in the N–N linker, were synthesized. With each ligand, two major isomers formed, and these were structurally assigned and characterized through a combination of NMR and UV–vis spectroscopies, X-ray crystallography, and density functional theory calculations. The <i>cis</i>-β geometric isomer was formed by each ligand, whereas the <i>trans</i> and <i>cis</i>-α geometric isomers were significant components for one ligand only. Cyclic voltammetry studies show that only the <i>cis</i>-β isomers undergo linkage isomerism upon oxidation to ruthenium­(III), whereas the <i>trans</i> and <i>cis</i>-α isomers show simple reversible redox couples