Singlet Fission in Lycopene H-Aggregates,The Journal of Physical Chemistry Letters

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Singlet Fission in Lycopene H-Aggregates
The Journal of Physical Chemistry Letters ( IF 4.8 ) Pub Date : 2023-10-27 , DOI: 10.1021/acs.jpclett.3c02435
William Barford ₁

Affiliation

A theory of singlet fission (SF) in carotenoid dimers is applied to explain the SF in lycopene H-aggregates observed after high-energy photoexcitation. The explanation proposed here is that a high energy, delocalized bright ¹B_u⁺ state first relaxes and localizes onto a single lycopene monomer. The high-energy intramonomer state then undergoes internal conversion to the 1¹B_u^– state. Once populated, the 1¹B_u^– state allows exothermic bimolecular singlet fission, while its internal conversion to the 2¹A_g^– state is symmetry forbidden. The simulation of SF predicts that the intramonomer triplet-pair state undergoes almost complete population transfer to the intermonomer singlet-pair state within 100 ps. Simultaneously, ZFS interactions begin to partially populate the intermonomer quintet triplet-pair state up to ca. 2 ns, after which hyperfine interactions thermally equilibrate the triplet-pair states, thus forming free single triplets within 50 ns.

中文翻译：

番茄红素 H 聚集体中的单线态裂变

应用类胡萝卜素二聚体中的单线态裂变 (SF) 理论来解释高能光激发后观察到的番茄红素 H 聚集体中的 SF。_这里提出的解释是，高能、离域明亮¹Bu ⁺态首先弛豫并定位到单个番茄红素单体上。然后高能单体内状态经历内部转化为 1 ¹B _u^–状态。一旦填充，1 ¹B _u^–态允许放热双分子单线态裂变，而其向 2 ¹A _g^–态的内部转换是对称禁止的。SF 模拟预测单体内三重态对状态在 100 ps 内几乎完全迁移到单体间单重态对状态。同时，ZFS 相互作用开始部分填充单体间五重态三重态对状态，最多可达约 100 倍。2 ns，之后超精细相互作用使三重态对态热平衡，从而在 50 ns 内形成自由的单三重态。

更新日期：2023-10-27

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