Lymar Sergei V, Ertem Mehmed Z, Lewandowska-Andralojc Anna, Polyansky Dmitry E
Chemistry Department, Brookhaven National Laboratory , Upton, New York 11973-5000, United States.
J Phys Chem Lett. 2017 Sep 7;8(17):4043-4048. doi: 10.1021/acs.jpclett.7b01614. Epub 2017 Aug 15.
Electron-proton transfer (EPT) from phenols to a triplet metal-to-ligand charge transfer (MLCT)-excited Ru polypyridine complex containing an uncoordinated nitrogen site, 1(T), can be described by a kinetic model that accounts for the H-bonding of 1(T) to phenol, 1(T) to solvent, and phenol to solvent. The latter plays a major role in the kinetic solvent effect and commonly precludes simultaneous determination of the EPT rate constant and 1(T)-phenol H-bonding constant. A number of these quantities previously reported for similar systems are shown to be in error due to inconsistent data analysis. Control experiments replacing either 1(T) by its structural isomer with a sterically screened nitrogen site or phenol by its H-bonding surrogate, trifluoroethanol, and the observation of negative activation enthalpies for the overall reactions between 1(T) and phenols lend support to the proposed model and provide evidence for the formation of a precursor H-bonded complex between the reactants, which is a prerequisite for EPT.
从酚类到含有未配位氮位点的三重态金属到配体电荷转移（MLCT）激发的钌多吡啶配合物1(T)的电子-质子转移（EPT），可以用一个动力学模型来描述，该模型考虑了1(T)与酚类、1(T)与溶剂以及酚类与溶剂之间的氢键作用。后者在动力学溶剂效应中起主要作用，通常会妨碍同时测定EPT速率常数和1(T)-酚类氢键常数。先前报道的类似体系的许多这些量由于数据分析不一致而被证明是错误的。用具有空间位阻屏蔽氮位点的结构异构体取代1(T)，或用其氢键替代物三氟乙醇取代酚类的对照实验，以及观察到1(T)与酚类之间整体反应的负活化焓，为所提出的模型提供了支持，并为反应物之间形成前体氢键复合物提供了证据，这是EPT的先决条件。
