Walia Rajat, Deng Zexiang, Yang Jun
Department of Chemistry, The University of Hong Kong Pokfulam Road Hong Kong P. R. China
Chem Sci. 2021 Aug 30;12(39):12928-12938. doi: 10.1039/d1sc01703a. eCollection 2021 Oct 13.
Singlet fission duplicates triplet excitons for improving light harvesting efficiency. The presence of the interaction between electronic and nuclear degrees of freedom complicates the interpretation of correlated triplet pairs. We report a quantum chemistry study on the significance and subtleties of multistate and multimode pathways in forming triplet pair states of the pentacene dimer through a six-state vibronic-coupling Hamiltonian derived from many-electron adiabatic wavefunctions of an density matrix renormalization group. The resulting spin values of the singlet manifolds on each pentacene center are computed, and the varying spin nature can be distinguished clearly with respect to dimer stacking and vibronic progression. Our monomer spin assignments reveal the coexistence of both lower-lying weak and higher-lying strong charge transfer states which interact vibronically with the triplet pair state, providing important implications for its generation and separation occurring in vibronic regions. This work conveys the importance of the many-electron process requiring close low-lying singlet manifolds to determine the subtle fission details, and represents an important step for understanding vibronically resolved spin states and conversions underlying efficient singlet fission.
单线态裂变可复制三线态激子，以提高光捕获效率。电子自由度与核自由度之间相互作用的存在，使得对相关三线态对的解释变得复杂。我们通过基于密度矩阵重整化群的多电子绝热波函数导出的六态振动耦合哈密顿量，报告了一项关于并五苯二聚体形成三线态对态过程中多态和多模路径的重要性及微妙之处的量子化学研究。计算了每个并五苯中心单线态流形的自旋值，并且可以根据二聚体堆积和振动进程清晰地区分不同的自旋性质。我们对单体自旋的分配揭示了低能级弱电荷转移态和高能级强电荷转移态的共存，它们与三线态对态发生振动相互作用，这对其在振动区域中的产生和分离具有重要意义。这项工作传达了多电子过程的重要性，该过程需要紧密的低能级单线态流形来确定微妙的裂变细节，并且代表了理解有效单线态裂变背后振动分辨的自旋态和转换的重要一步。
