We investigate the dynamical interplay between the different triplet-pair spin states that are formed in the intramolecular singlet fission process in a series of pentacene-based dimers covalently bonded to a phenylene linker in ortho, meta, and para positions. Using first-principles calculations and a density matrix quantum dynamical approach we show that the spin dipole–dipole interaction leads to significant population of the quintet spin manifold in these regioisomers when the singlet, triplet and quintet triplet-pair states are quasidegenerate. Furthermore, we also show that the relative arrangement of the pentacene-like moieties has a profound impact on the dynamics of the spin-mixing process, affecting both the relative population of the different spin-states involved in the dynamics and the time scale of the process.

中文翻译：

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分子内单线态裂变中的自旋混合：基于第一性原理的量子动力学研究


我们研究了在分子内单线态裂变过程中形成的不同三重态对自旋态之间的动力学相互作用，这些二聚体在一系列基于五苯的二聚体中以邻位、间位和对位共价键合到苯基连接子上。使用第一性原理计算和密度矩阵量子动力学方法，我们表明，当单重态、三重态和五重态三重态对态是四侧生成时，自旋偶极子-偶极子相互作用导致这些区域异构体中五重体自旋流形的大量数量。此外，我们还表明，类五苯部分的相对排列对自旋混合过程的动力学有深远的影响，影响动力学中涉及的不同自旋态的相对数量和过程的时间尺度。