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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Photoreduction of 4,4'-Bipyridine by Amines in Acetonitrile-Water Mixtures:Influence of H-Bonding on the Ion-Pair Structure and Dynamics
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Photoreduction of 4,4'-Bipyridine by Amines in Acetonitrile-Water Mixtures:Influence of H-Bonding on the Ion-Pair Structure and Dynamics

机译：乙腈-水混合物中的胺对4,4'-联吡啶的光还原作用：氢键对离子对结构和动力学的影响

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摘要

The photoreduction of 4,4'-bipyridine (44BPY) by diazabicyclo[2.2.2]octane and triethylamine (TEA) is investigated by using picosecond transient absorption and time-resolved resonance Raman spectroscopy in various acetonitrile-water mixtures.The results are interpreted on the basis of a preferential solvation effect resulting from the presence of a specific interaction between 44BPY and water by hydrogen bonding.Below 10% water,the free 44BPY species is dominant and leads upon photoreduction to a contact ion pair that undergoes efficient intrapair proton transfer if TEA is the amine donor.Above 10% water,most of the 44BPY population is H-bonded and leads upon photoreduction to a hydrated ion pair in which the intrapair proton transfer is inhibited.Instead,the 44BPY~(- centre dot) species is protonated by water through the hydrogen bond with a rate constant that increases by more than 3 orders of magnitude on going from 10% to 100% water.The dependence of this rate constant on the solvent mixture composition suggests that the reaction of intracomplex proton transfer is controlled by the hydration of the residual OH~- species by three molecules of water,leading to a trihydrated HO~-(H_2O)_3 species.
机译：利用皮秒瞬态吸收和时间分辨共振拉曼光谱研究了乙腈-水混合物中二氮杂双环[2.2.2]辛烷和三乙胺（TEA）对4,4'-联吡啶（44BPY）的光还原作用。在44BPY和水之间通过氢键存在特异性相互作用而产生的优先溶剂化作用的基础上。低于10％的水，游离的44BPY物质占主导地位，并在光还原后导致接触离子对经过有效的对内质子转移如果TEA是胺供体，则在10％的水上，大多数44BPY种群是H键合的，并且在光还原后导致水合离子对的发生，从而抑制了对内质子转移.44BPY〜（-中心点）物种通过氢键使水质子化，其速率常数在水从10％变为100％时增加3个数量级以上。该混合物的组成表明，复杂分子内质子转移的反应是由三分子水将残留的OH〜-分子水合而控制的，从而生成三水合的HO〜-（H_2O）_3物种。

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