Sláma Vladislav, Perlík Václav, Langhals Heinz, Walter Andreas, Mančal Tomáš, Hauer Jürgen, Šanda František
Institute of Physics, Faculty of Mathematics and Physics, Charles University, Prague, Czechia.
Department of Chemistry, Ludwig-Maximilians-Universität München, Munich, Germany.
Front Chem. 2020 Nov 23;8:579166. doi: 10.3389/fchem.2020.579166. eCollection 2020.
Spectral and dynamical properties of molecular donor-acceptor systems strongly depend on the steric arrangement of the constituents with exciton coupling as a key control parameter. In the present work we study two arylene based dyads with orthogonal and parallel transition dipoles for donor and acceptor moieties, respectively. We show that the anharmonic multi-well character of the orthogonal dyad's intramolecular potential explains findings from both stationary and time-resolved absorption experiments. While for a parallel dyad, standard quantum chemical estimates of at 0 K are in good agreement with experimental observations, becomes vanishingly small for the orthogonal dyad, in contrast to its ultrafast experimental transfer times. This discrepancy is not resolved even by accounting for harmonic fluctuations along normal coordinates. We resolve this problem by supplementing quantum chemical approaches with dynamical sampling of fluctuating geometries. In contrast to the moderate Gaussian fluctuations of for the parallel dyad, fluctuations for the orthogonal dyad are found to follow non-Gaussian statistics leading to significantly higher effective in good agreement with experimental observations. In effort to apply a unified framework for treating the dynamics of optical coherence and excitonic populations of both dyads, we employ a vibronic approach treating electronic and selected vibrational degrees on an equal footing. This vibronic model is used to model absorption and fluorescence spectra as well as donor-acceptor transport dynamics and covers the more traditional categories of Förster and Redfield transport as limiting cases.
分子供体 - 受体系统的光谱和动力学性质强烈依赖于其组成部分的空间排列，其中激子耦合是关键控制参数。在本工作中，我们研究了两种基于亚芳基的二元体系，其供体和受体部分分别具有正交和平行的跃迁偶极矩。我们表明，正交二元体系分子内势的非谐多阱特性解释了稳态和时间分辨吸收实验的结果。对于平行二元体系，0 K时的标准量子化学估计值与实验观测结果吻合良好，而对于正交二元体系，尽管其超快的实验转移时间，但 变得极小。即使考虑沿正常坐标的谐波涨落，这种差异也无法解决。我们通过对波动几何结构进行动态采样来补充量子化学方法，从而解决了这个问题。与平行二元体系适度的高斯涨落不同，正交二元体系的涨落遵循非高斯统计，导致有效 显著更高，这与实验观测结果吻合良好。为了应用一个统一的框架来处理两个二元体系的光学相干和激子布居动力学，我们采用了一种将电子和选定振动自由度同等对待的振子方法。这个振子模型用于模拟吸收和荧光光谱以及供体 - 受体传输动力学，并涵盖了更传统的Förster和Redfield传输类别作为极限情况。
