光敏化反应生成单线态氧的电子耦合计算及共分子轨道重叠描述

Electronic Couplings for Singlet Oxygen Photosensitization and Its Molecular Orbital Overlap Description

三重态融合反应又称三重态-三重态湮灭反应,近年来被广泛应用于光催化、太阳能电池和生物成像等前沿领域.在光敏化生成单线态氧的反应中,三重态激发的光敏剂分子通过三重态融合反应将激发态能量传递给基态氧分子^(3)O_(2),生成单重态的激发氧分子即单线态氧.本文以6-aza-2-thiothymine为光敏剂,通过量子化学计算得到该反应的非绝热耦合强度,然后通过分子间运动下的积分转换,得到反应的透热电子耦合强度.最后使用光敏剂分子和O_(2)的前线分子轨道计算轨道重叠强度,对量子化学计算得到的电子耦合值进行拟合,验证三重态融合反应的分子轨道重叠描述.结果表明,分子轨道重叠可以较好地描述不同间距下光敏剂-O_(2)三线态融合反应的电子耦合强度分布,为预测三重态融合反应电子耦合提供了一种简便而有效的新方法.

The reaction of triplet fusion,also named triplet-triplet annihilation,has attracted a lot of research interests because of its wide applications in photocatalytic,solar cells,and bioimaging.As for the singlet oxygen photosensitization,the reactive singlet oxygen species are generated through the energy transfers from photosensitizer(PS)to ground triplet oxygen molecule.In this work,we computed the electronic coupling for singlet oxygen photosensitization using the nonadiabatic coupling from the quantum chemical calculation.Then we utilized the molecular orbital(MO)overlaps to approximate it,where the MOs were computed from isolated single molecules.As demonstrated with quantitative results,this approach well describes the distribution of the coupling strength as the function of the intermolecular distance between the sensitizer and O_(2),providing us a simple but effective way to predict the coupling of triplet fusion reactions.