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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Hydrogen-bond strengthening upon photoinduced electron transfer in ruthenium-anthraquinone dyads interacting with hexafluoroisopropanol or water
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Hydrogen-bond strengthening upon photoinduced electron transfer in ruthenium-anthraquinone dyads interacting with hexafluoroisopropanol or water

机译：与六氟异丙醇或水相互作用的钌-蒽醌二联体中光诱导电子转移的氢键强化

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摘要

Quinones play a key role as primary electron acceptors in natural photosynthesis, and their reduction is known to be facilitated by hydrogen-bond donors or protonation. In this study, the influence of hydrogen-bond donating solvents on the thermodynamics and kinetics of intramolecular electron transfer between Ru(bpy) _3 ~(2+) (bpy = 2,2′-bipyridine) and 9,10-anthraquinone redox partners linked together via one up to three p-xylene units was investigated. Addition of relatively small amounts of hexafluoroisopropanol to dichloromethane solutions of these rigid rodlike donor-bridge-acceptor molecules is found to accelerate intramolecular Ru(bpy) _3 ~(2+)-to-anthraquinone electron transfer substantially because anthraquinone reduction occurs more easily in the presence of the strong hydrogen-bond donor. Similarly, the rates for intramolecular electron transfer are significantly higher in acetonitrile/water mixtures than in dry acetonitrile. In dichloromethane, an increase in the association constant between hexafluoroisopropanol and anthraquinone by more than 1 order of magnitude following quinone reduction points to a significant strengthening of the hydrogen bonds between the hydroxyl group of hexafluoroisopropanol and the anthraquinone carbonyl functions. The photoinduced intramolecular long-range electron transfer process thus appears to be followed by proton motion; hence the overall photoinduced reaction may be considered a variant of stepwise proton-coupled electron transfer (PCET) in which substantial proton density (rather than a full proton) is transferred after the electron transfer has occurred.
机译：醌在自然光合作用中作为主要电子受体发挥关键作用，已知氢键供体或质子化促进了醌的还原。在这项研究中，氢键给体溶剂对Ru（bpy）_3〜（2+）（bpy = 2,2'-联吡啶）和9,10-蒽醌氧化还原伙伴之间分子内电子转移的热力学和动力学的影响研究了通过多达三个对二甲苯单元连接在一起的情况。发现将相对少量的六氟异丙醇添加到这些刚性棒状供体桥受体分子的二氯甲烷溶液中，可促进分子内Ru（bpy）_3〜（2+）向蒽醌的电子转移，这主要是因为蒽醌的还原更容易在强氢键供体的存在。类似地，乙腈/水混合物中分子内电子转移的速率明显高于干乙腈。在二氯甲烷中，醌还原后六氟异丙醇和蒽醌之间的缔合常数增加大于1个数量级，表明六氟异丙醇的羟基和蒽醌羰基官能团之间的氢键显着增强。因此，光诱导的分子内远距离电子转移过程似乎伴随着质子运动。因此，整个光诱导反应可被认为是逐步质子耦合电子转移（PCET）的变体，其中电子转移发生后，大量的质子密度（而不是完整的质子）转移了。

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