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Density functional theory (DFT) calculations were performed to elucidate the mechanism of the dehydrogenative oxidation of various primary alcohols (or α-hydroxy carboxylic acids) and the dehydrogenative coupling of alcohols with ammonia catalysed by the same water-soluble Cp*Ir complex bearing a 2-pyridonate-based ligand (A–Ir). Another two new catalysts A–Rh and A–Os are computationally designed for the dehydrogenative oxidation of alcohols. The plausible pathway for alcohol dehydrogenation includes three steps: alcohol oxidation to aldehyde (step I); the generation of dihydrogen in the metal coordination sphere (step II); and the liberation of dihydrogen accompanied with the regeneration of active catalyst A (step III). Among them, the step I follows bifunctional concerted double hydrogen transfer mechanism rather than the β-H elimination. For step II, the energy barriers involving the addition of one or two water molecules are higher than in absence of water. Our results also confirm that A–Ir can be ...

The effect of substitution and cooperativity on the blue shift of Cl–F stretch vibration in H3C ··· ClF complex has been studied with quantum chemical calculations at the UMP2(Full)/aug-cc-pVTZ level. The electron-withdrawing group (F atom) in the electron donor decreases the blue shift, whereas the electron-donating group (methyl group) in the electron donor cause it to increase. The cooperativity between two different types of halogen bonds in H3C ··· ClF ··· ClF complex enhances the strength of single-electron halogen bond and the blue shift. The natural bond orbital (NBO) and atoms in molecules (AIM) analyses have been performed for the halogen-bonded complexes.

Various levels of calculations are carried out to explore the potential energy surfaces (PES) of singlet and triplet SiC3S, a molecule of potential interest in interstellar chemistry. At the DFT/B3LYP/6-311G(d) level, a total of 57 minimum isomers and 92 interconversion transition states are located. The structures of the most relevant isomers and transition states are further optimized at the QCISD/6-311G(d) level followed by CCSD(T)/6-311 + G(2df) single-point energy calculations. At the QCISD level, the lowest-lying isomer is the chain-like SiCCCS 3 1 (0.0 kcal/mol) with a great kinetic stability of 54.1 kcal/mol. In addition, ring isomers CC-cCSSi 1 9 (19.8 kcal/mol), S-cCCCSi 1 12 (30.4 kcal/mol), S-cCCSiC 1 18 (9.4 kcal/mol), S-cSiCCC 1 21 (34.4 kcal/mol) and cage-like isomer cage-SiSCCC 1 23 (51.8 kcal/mol) also possess considerable kinetic stability (more than 10.0 kcal/mol). As a result, these six isomers are predicted to be possible candidates for future experimental and astrophysical detection....