Scuola Normale Superiore, Pisa 56126, Italy.
Università degli studi di Padova, Padova 35122, Italy.
J Chem Phys. 2021 Mar 7;154(9):094110. doi: 10.1063/5.0039949.
The non-radiative relaxation process within the Q-bands of chlorophylls represents a crucial preliminary step during the photosynthetic mechanism. Despite several experimental and theoretical efforts performed in order to clarify the complex dynamics characterizing this stage, a complete understanding of this mechanism is still far to be reached. In this study, non-adiabatic excited-state molecular dynamic simulations have been performed to model the non-radiative process within the Q-bands for a model system of chlorophylls. This system has been considered in the gas phase and then, to have a more representative picture of the environment, with implicit and mixed implicit-explicit solvation models. In the first part of this analysis, absorption spectra have been simulated for each model in order to guide the setup for the non-adiabatic excited-state molecular dynamic simulations. Then, non-adiabatic excited-state molecular dynamic simulations have been performed on a large set of independent trajectories and the population of the Q and Q states has been computed as the average of all the trajectories, estimating the rate constant for the process. Finally, with the aim of investigating the possible role played by the solvent in the Q-Q crossing mechanism, an essential dynamic analysis has been performed on the generated data, allowing one to find the most important motions during the simulated dynamics.
叶绿素 Q 带内的非辐射弛豫过程是光合作用机制中的一个关键初步步骤。尽管已经进行了多次实验和理论努力来阐明描述这一阶段的复杂动力学，但对这一机制的全面理解仍远未实现。在这项研究中，进行了非绝热激发态分子动力学模拟，以模拟叶绿素模型系统中 Q 带内的非辐射过程。该系统在气相中进行了考虑，然后，为了更具代表性地描述环境，使用了隐式和混合隐式-显式溶剂化模型。在分析的第一部分中，为每个模型模拟了吸收光谱，以指导非绝热激发态分子动力学模拟的设置。然后，在大量独立轨迹上进行了非绝热激发态分子动力学模拟，并通过所有轨迹的平均值计算了 Q 和 Q 态的布居，从而估算了该过程的速率常数。最后，为了研究溶剂在 Q-Q 交叉机制中可能发挥的作用，对生成的数据进行了重要的动态分析，从而可以找到模拟动力学过程中最重要的运动。
