The singlet fission (SF) channels in many systems are controlled by the thermodynamic driving force (Switch 1) and kinetic barrier (Switch 2) both of which could be modulated by chromophore structure dynamics and solvent properties because they can cause chromophore different transient photoexcitation energetics. In this work, using ab initio molecular dynamics (AIMD) samplings, we simulate how the structural dynamics and solvent impact jointly govern the singlet pre-fission energetics, taking a T-shaped covalent BODIPY dimer (di-BODIPY, not meeting the SF criterion in the gas phase) in polar CHCl3 and apolar cyclohexane as examples. We report a general dual-switched dynamic channel for intramolecular SF in solvents which can reasonably interpret the complicated SF phenomena and also suggest an effective AIMD sampling method to characterize the joint effect of chromophore structure dynamics and solvent impact on SFs. Results reveal that structural fluctuation and solvent impact not only cooperatively provide di-BODIPY more chances for meeting the SF thermodynamic requirement in solvents (Switch 1 ON), but also jointly tune the charge transfer state towards removing the kinetic barrier (Switch 2 ON). Two factors jointly govern each switch and thus the dynamic dual-switched SF channel in di-BODIPY and anyone doesn't open the channel alone. We suggest a general principle for dynamically dual-switching the SF channel in solvents by utilizing structural dynamics of chromophore and impact of solvents to tune the pre-SF energetics of chromophore for photoexcitation and opening of the subsequent channel. We for the first time propose the AIMD sampling to get detailed explicit solvent/solute interaction information and structure dynamics of chromophore and their effect on the excitation energetics. This work also shows the statistic information for an ensemble of the SF chromophores in solvents which can undergo different photoexcitations and possible subsequent SFs. High agreement of the findings here with experiments justifies our AIMD-sampling-based pre-SF energetic prediction to be a reliable way for exploring novel SF systems and their controllability.

中文翻译：

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由发色团结构动力学和溶剂影响共同控制的溶剂中的一般双切换动态单线态裂变通道：单线态预裂变能量分析

许多系统中的单线态裂变 (SF) 通道由热力学驱动力 (开关 1) 和动力学势垒 (开关 2) 控制，两者都可以通过发色团结构动力学和溶剂性质进行调节，因为它们会导致发色团不同的瞬态光激发能量. 在这项工作中，使用从头分子动力学 (AIMD) 采样，我们模拟了结构动力学和溶剂影响如何共同控制单线态裂变前能量学，采用 T 形共价 BODIPY 二聚体（di-BODIPY，不符合 SF 标准）在气相中）在极性 CHCl3 和非极性环己烷中作为例子。我们报告了溶剂中分子内 SF 的一般双开关动态通道，它可以合理地解释复杂的 SF 现象，并提出一种有效的 AIMD 采样方法来表征发色团结构动力学和溶剂对 SF 影响的联合效应。结果表明，结构波动和溶剂影响不仅共同为 di-BODIPY 提供了更多满足溶剂中 SF 热力学要求的机会（开关 1 打开），而且还共同调整电荷转移状态以消除动力学障碍（开关 2 打开）。两个因素共同控制每个开关，因此 di-BODIPY 中的动态双开关 SF 通道，任何人都不会单独打开通道。我们提出了一种通用原理，通过利用发色团的结构动力学和溶剂的影响来调整发色团的前 SF 能量以进行光激发和后续通道的打开，从而动态地双切换溶剂中的 SF 通道。我们首次提出 AIMD 采样以获得详细的显式溶剂/溶质相互作用信息和发色团的结构动力学及其对激发能量学的影响。这项工作还显示了溶剂中 SF 发色团集合的统计信息，这些发色团可以经历不同的光激发和可能的后续 SF。这里的发现与实验的高度一致证明我们基于 AIMD 采样的前 SF 能量预测是探索新型 SF 系统及其可控性的可靠方法。