揭示无重原子光敏剂中三重态形成的机制
Unraveling the mechanisms of triplet state formation in a heavy-atom free photosensitizer
AI总结：
本研究通过第一性原理模型揭示了无重原子BD-An光敏剂中竞争性量子效应驱动高效三重态形成的机制，并阐明了自旋-轨道耦合与系间窜越的关键作用。
摘要：
三重激发态的生成在光敏剂中起着关键作用，但对过渡金属和重原子的依赖限制了这些体系的实用性。在本研究中，我们证明了竞争性量子效应的相互作用控制了典型硼二吡咯亚甲基-蒽（BD-An）给体-受体二联体光敏剂中的高三重态量子产率，这仅通过对内层和外层重组能的精确处理才能捕捉到。我们基于第一性原理推导的模型与实验测量的光谱、三重态产率和激发态动力学数据（包括三重态寿命）高度一致。我们发现，快速的三重态形成主要通过高能三重态发生，涉及自旋-轨道耦合电荷转移和违反El-Sayed定则的系间窜越，而非直接的自旋-轨道耦合电荷转移至最低三重态。计算还揭示了核隧穿、电子态重交叉和电子极化率的竞争效应主导了非生产性基态复合的速率。本研究阐明了驱动BD-An体系高效三重态形成的量子效应，并为多种光化学体系提供了有前景的模拟方法。
英文摘要：
Triplet excited state generation plays a pivotal role in photosensitizers, however the reliance on transition metals and heavy atoms can limit the utility of these systems. In this study, we demonstrate that an interplay of competing quantum effects control the high triplet quantum yield in a prototypical boron dipyrromethene-anthracene (BD-An) donor-acceptor dyad photosensitizer, which is only captured by an accurate treatment of both inner and outer sphere reorganization energies. Our ab initio-derived model provides excellent agreement with experimentally measured spectra, triplet yields and excited state kinetic data, including the triplet lifetime. We find that rapid triplet state formation occurs primarily via high-energy triplet states through both spin-orbit coupled charge transfer and El-Sayed's rule breaking intersystem crossing, rather than direct spin-orbit coupled charge transfer to the lowest lying triplet state. Our calculations also reveal that competing effects of nuclear tunneling, electronic state recrossing, and electronic polarizability dictate the rate of non-productive ground state recombination. This study sheds light on the quantum effects driving efficient triplet formation in the BD-An system, and offers a promising simulation methodology for diverse photochemical systems.
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