Hong Yongseok, Kim Juno, Kim Dongho, Kim Hyungjun
Department of Chemistry, Spectroscopy Laboratory for Functional π-Electronic Systems, Yonsei University, Seoul 03722, Republic of Korea.
Department of Chemistry, Quantum Chemistry Laboratory, Incheon National University, 119 Academy-ro, Yeonsu-gu, Incheon 22012, Republic of Korea.
J Phys Chem A. 2021 Jan 28;125(3):875-884. doi: 10.1021/acs.jpca.0c08706. Epub 2021 Jan 13.
We investigated the potential of chromophore's rotations to tune singlet fission (SF) kinetics in perylene bisimide (PBI) dimers in addition to relative horizontal displacements. The total number of 250 PBI dimers (five displacements along the long and short axis of PBI, respectively, and ten rotation angle changes from parallel to perpendicular alignment) was examined. Ground-state energies showed that dimer formation is favored in all orientations with some differences in interaction strength. Time-dependent density functional theory predicted S and T excitons' energy, and the thermodynamic feasibility of SF process was judged by the energy difference between a S exciton and twice of T excitons. In addition, we also estimated the relative rate of multiexciton generation step by the three-state kinetic model with the results of restricted active space employing double spin-flip. Nine promising orientations including two parallel PBI dimers and seven twisted ones were discussed. Wave function composition analysis showed that SF occurs mainly through the superexchange mechanism in various twisted PBI dimers, but the direct two-electron and coherent pathway could be operative at the particular positions. Quantum chemical simulations suggested the rotation as an effective tool to tune SF efficiency in PBI dimers, which is helpful to substantiate more efficient SF material.
我们研究了除相对水平位移外，发色团旋转调节苝二酰亚胺（PBI）二聚体中单线态裂变（SF）动力学的潜力。研究了总共250个PBI二聚体（分别沿PBI的长轴和短轴有五个位移，以及从平行到垂直排列有十个旋转角度变化）。基态能量表明，在所有取向中都有利于二聚体形成，只是相互作用强度存在一些差异。含时密度泛函理论预测了单重态和三重态激子的能量，并通过单重态激子与两倍三重态激子之间的能量差来判断SF过程的热力学可行性。此外，我们还利用双自旋翻转的受限活性空间结果，通过三态动力学模型估计了多激子产生步骤的相对速率。讨论了九个有前景的取向，包括两个平行的PBI二聚体和七个扭曲的二聚体。波函数组成分析表明，在各种扭曲的PBI二聚体中，SF主要通过超交换机制发生，但在特定位置可能存在直接双电子和相干途径。量子化学模拟表明，旋转是调节PBI二聚体中SF效率的有效工具，这有助于证实更高效的SF材料。
