Redox potentials of trifluoromethyl-containing compounds

Trifluoromethylation reactions are important transformations in the research and development of drugs, agrochemicals and functional materials. An oxidation/reduction process of trifluoromethyl-containing compounds is thought to be involved in many recently tested catalytic trifluoromethylation reactions. To provide helpful physical chemical data for mechanistic studies on trifluoromethylation reactions, the redox potentials of a variety of trifluoromethyl-containing compounds and trifluoro- methylated radicals were studied by quantum-chemical methods. First, eoB97X-D was found to be a reliable method in predicting the ionization potentials, electron affinities, bond dissociation enthalpies and redox potentials of trifluoromethylcontaining compounds. One-electron absolute redox potentials of 79 trifluoromethyl substrates and 107 trifluoromethylated radicals in acetonitrile were then calculated with this method. The theoretical results were found to be helpful for interpreting experimental observations such as the relative reaction efficiency of different trifluoromethylation reagents. Finally, the bond dissociation free energies （BDFE） of various compounds were found to have a good linear relationship with the related bond dissociation enthalpies （BDE）. Based on this observation, a convenient method was proposed to predict one-electron redox potentials of neutral molecules.

Engineering the grain boundary:a promising strategy to configure NiCoP_(4)O_(12)/NiCoP nanowire arrays for ultra-stable supercapacitor

NiCoP_(4)O_(12)/NiCoP nanorod-like arrays with tunable grain boundary density and pores were synthesized by the processes composed of hydrothermal and pyrolysis,in which,the electron structure of Ni and Co atoms characterized by X-ray photoelectron spectroscopy was contemporaneous inverse manipulated.The optimized NiCoP_(4)O_(12)/NiCoP arrays have a high specific capacitance of 507.8μAh∙cm^(–2)at 1 mA∙cm^(–2),and good rate ability of 64.7%retention at 30-folds increased current density.Importantly,an ultra-stable ability,88.5%of retention after 10000 cycles,was achieved in an asymmetric cell assembled of the NiCoP_(4)O_(12)/NiCoP arrays with activated carbon.In addition,the energy and power densities of an asymmetric cell were higher than those of other work,demonstrating as-prepared NiCoP_(4)O_(12)/NiCoP arrays are promising electrodes for supercapacitors.

Mechanism of N-to-S acyl transfer of N-(2-hydroxybenzyl) cysteine derivatives and origin of phenol acceleration effect

N-（2-Hydroxybenzyl）cysteine derivatives were recently disclosed to be efficient crypto-thioesters for native chemical ligation（NCL）. To elucidate the mechanism of the relevant N-to-S acyl transfer process as well as the origin of the acceleration effect of the phenol substitutes, a density functional theory（DFT）study was performed. It was found that the N-to-S acyl transfer of N-（2-hydroxybenzyl）cysteine derivatives involve four major steps： concerted nucleophilic addition of thiolate/proton transfer,inversion of an amine moiety, water-assisted proton transfer and CààN bond cleavage. The phenol substitutes promote the nucleophilic addition of thiolate by protonating the carbonyl oxygen atom synergistically and the proton transfer from hydroxyl to amide nitrogen atom is the rate-determining step of the N-to-S acyl transfer. By contrast, changing the phenolic hydroxyl to methoxyl was found to significantly slow down the nucleophilic addition of thiolate and thus hinders the N-to-S acyl transfer overall. These computational results are consistent with the observation of previously reported control experiments, by which our proposed mechanism is further validated.