Cui Kai, Hammes-Schiffer Sharon
Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States.
J Am Chem Soc. 2025 Jun 25;147(25):21708-21717. doi: 10.1021/jacs.5c03866. Epub 2025 Jun 10.
Proton-coupled energy transfer (PCEnT) refers to a photochemical process in which the transfer of electronic excitation energy between donor and acceptor molecules is coupled to a proton transfer reaction. Herein, we apply our recently developed nonadiabatic PCEnT theory to an anthracene-phenol-pyridine triad system. For this system, electronic excitation energy is transferred from the anthracene to the phenol-pyridine, in conjunction with proton transfer from the phenol to the pyridine. Thus, the PCEnT reaction corresponds to the transition from the local excited state of the anthracene (LES) to the local electron-proton transfer (LEPT) state of the phenol-pyridine. With most input quantities determined from first-principles calculations, our theory reproduces the experimentally measured PCEnT rate constant. We analyzed the contributions from different electron-proton vibronic states to the PCEnT rate constant (the LES to LEPT state) and the acceptor absorption spectrum (the ground state to LEPT state). For the triad, PCEnT occurs in the absence of detectable spectral overlap between the donor emission and acceptor absorption spectra, even though conventional energy transfer theories require adequate spectral overlap. In this case, the LEPT vibronic state that dominates the PCEnT process contributes negligibly to the acceptor absorption spectrum due to the small Franck-Condon overlap associated with proton transfer. Energy transfer in PCEnT requires accompanying proton transfer to lower the energy of the LEPT state and enable sufficient spectral overlap that overcomes the small proton vibrational wave function overlap associated with proton transfer. This work enhances fundamental understanding of the PCEnT process and provides guidance for the design of other types of PCEnT systems.
质子耦合能量转移（PCEnT）是指一种光化学过程，其中供体和受体分子之间的电子激发能转移与质子转移反应相耦合。在此，我们将最近开发的非绝热PCEnT理论应用于蒽-苯酚-吡啶三联体系。对于该体系，电子激发能从蒽转移至苯酚-吡啶，同时伴随着质子从苯酚转移至吡啶。因此，PCEnT反应对应于从蒽的局域激发态（LES）到苯酚-吡啶的局域电子-质子转移（LEPT）态的转变。由于大多数输入量由第一性原理计算确定，我们的理论再现了实验测量的PCEnT速率常数。我们分析了不同电子-质子振动态对PCEnT速率常数（从LES到LEPT态）和受体吸收光谱（从基态到LEPT态）的贡献。对于该三联体，即使传统能量转移理论要求有足够的光谱重叠，但在供体发射光谱和受体吸收光谱之间不存在可检测到的光谱重叠的情况下，PCEnT仍会发生。在这种情况下，主导PCEnT过程的LEPT振动态对受体吸收光谱的贡献可忽略不计，这是因为与质子转移相关的弗兰克-康登重叠较小。PCEnT中的能量转移需要伴随质子转移以降低LEPT态的能量，并实现足够的光谱重叠，从而克服与质子转移相关的小质子振动波函数重叠。这项工作增进了对PCEnT过程的基本理解，并为设计其他类型的PCEnT系统提供了指导。
