Intersystem Crossing in Tetrapyrrolic Macrocycles. A First-Principles Analysis
Intersystem Crossing in Tetrapyrrolic Macrocycles. A First-Principles Analysis
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DOI：
10.1021/acs.jpcc.1c03696
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发表时间：
2021-06-10
影响因子：
3.7
通讯作者：
Dunietz, Barry D.
中科院分区：
文献类型：
--
作者：
Bhandari, Srijana;Sarkar, Sunandan;Dunietz, Barry D.
我们分析了一系列具有不同饱和程度的四吡咯大环的光物理性质的报道趋势。我们比较了系统间交叉(ISC)和荧光在卟啉(P)、氯(CH)和细菌素(BC)中的光吸收速率。CH和BC分别是P的单氢化和双氢化的产物。基于一种新的框架，利用第一性原理含时密度泛函理论实现了量子力学费米黄金规则(FGR)速率理论。我们采用了最近发展起来的屏蔽程分离杂化(SRSH)泛函和可极化连续介质模型(PCM)来实现对嵌入分子电子结构的极化一致性描述。我们发现，与测量结果一致的是，氢化的ISC速率的增加源于自旋-轨道耦合(SOC)的增加。这一趋势可以追溯到相应的单线态和三线态的附着和剥离密度的重叠。与此同时，我们发现与ISC竞争的荧光速率增加，这总体上导致了较低的ISC产率，随着氢化程度的增加，尽管SOC增加。重要的是，FGR理论中的量子力学观点和DFT计算中使用的屏蔽RSH所实现的偏振一致性公式都是实现计算速率的预测质量所必需的。
We analyze reported trends of the photophysical properties in a series of tetrapyrrolic macrocycles with varied saturation level. We compare rates of intersystem crossing (ISC) and fluorescence upon photoabsorption in porphine (P), chlorin (CH), and bacteriochlorin (BC). CH and BC result from single hydrogenation and double hydrogenation of P, respectively. A first-principles time-dependent density functional theory based on a novel framework is used to implement a quantum-mechanical Fermi's golden rule (FGR) rate theory. We employ the recently developed screened range-separated hybrid (SRSH) functionals and a polarizable continuum model (PCM) achieving a polar- ization-consistent description of the embedded molecular electronic structure. We find, in agreement with the measurements, an increase of the ISC rate upon hydrogenation originating in an increase of the spin-orbit coupling (SOC). This trend is traced back to the overlap of attachment and detachment densities of the relevant singlet and triplet states. Simultaneously, we find an increase in the fluorescence rate competing with the ISC, which, overall, results in a lower ISC yield with increasing degree of hydrogenation despite the increased SOC. Crucially, both the quantum mechanical perspective in the FGR theory and the polarization consistent formulation achieved by the screened RSH used in the DFT calculations are required for achieving predictive quality in the calculated rates.