Solvent effect on electron and proton transfer in the excited state of a hydrogen bonded phenol–imidazole complex
Solvent effect on electron and proton transfer in the excited state of a hydrogen bonded phenol–imidazole complex
复制标题
溶剂对氢键苯酚-咪唑配合物激发态电子和质子转移的影响
作者：
B. Kang;Hu Shi;Shihai Yan;J. Lee
作为光系统II活性位点的模型系统，对氢键苯酚和咪唑配合物的基态（S0）和第一激发态（S1）进行了密度泛函理论计算。获得了S0和S1沿质子转移坐标的势能面（PES）。基于质子转移的相对稳定性和较小的能垒，发现质子转移在真空和水中都可以在激发态下发生。正如电荷分布所证实的，质子转移被确定为在真空中与电子转移（PCET）耦合，而不是在水中。这种现象应该源于溶剂效应稳定具有大偶极矩的π*态，从而导致产物结构不同。
Density functional theory calculations have been carried out for the ground state (S0) and the first excited state (S1) of the H-bonded phenol and imidazole complex as a model system for the active site of photosystem II. Potential energy surfaces (PES) of S0 and S1 along the proton transfer coordinate were obtained. Based on the relative stability and small energy barrier for proton transfer, it was found that proton transfer could take place in the excited state both in vacuum and in water. As confirmed by the charge distribution, the proton transfer is determined to be coupled with electron transfer (PCET) in vacuum, while not in water. Such phenomenon should originate from the solvent effect stabilizing π* state with a large dipole moment, which results in a different structure of the product.