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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Photophysical Heavy-Atom Effect in Iodinated Metallocorroles: Spin-Orbit Coupling and Density of States
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Photophysical Heavy-Atom Effect in Iodinated Metallocorroles: Spin-Orbit Coupling and Density of States

机译：在碘化的Metallocorles中的光药重原子作用：旋转轨道耦合和状态密度

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摘要

Excited-state dynamics and electronic structures of Al and Ga corrole complexes were studied as a function of the number of beta-pyrrole iodine substituents. Using spectrally broad-band femtosecond-resolved fluorescence upconversion, we determined the kinetics of the Soret fluorescence decay, the concomitant rise and subsequent decay of the Q-band fluorescence, as well as of the accompanying vibrational relaxation. Iodination was found to accelerate all involved processes. The time constant of the internal conversion from the Soret to the Q states decreases from 320-540 to 70-185 fs upon iodination. Vibrational relaxation then occurs with about 15 and 0.36-1.4 ps lifetime for iodine-free and iodinated complexes, respectively. Intersystem crossing to the lowest triplet is accelerated up to 200 times from nanoseconds to 15-24 ps; its rate correlates with the iodine p(pi) participation in the corrole pi-system and the spin-orbit coupling (SOC) strength. TDDFT calculations with explicit SOC show that iodination introduces a manifold of low-lying singlet and triplet iodine - corrole charge-transfer (CT) states. These states affect the photophysics by (i) providing a relaxation cascade for the Soret - Q internal conversion and cooling and (ii) opening new SOC pathways whereby CT triplet character is admixed into both Q-singlet excited states. In addition, SOC between the higher Q singlet and the Soret triplet is enhanced as the iodine participation in frontier corrole pi-orbitals increases. Our observations that iodination of the chromophore periphery affects the whole photocycle by changing the electronic structure, spin-orbit coupling, and the density of states rationalize the "heavy-atom effect" and have implications for controlling excited-state dynamics in a range of triplet photosensitizers.
机译：激发态动力学和Al和Ga corrole复合物的电子结构进行了研究作为β-内吡咯碘取代基的数目的函数。使用频谱宽带飞秒分辨荧光上转换，我们确定索瑞荧光衰减，随之而来的上升和Q带荧光的后续衰减的动力学，以及的伴随振动放松。碘化被发现加速所有参与的过程。从索瑞到Q态的内部转换的时间常数直接从碘化320-540到70-185 fs的下降。振动弛豫然后用约15和0.36-1.4 ps的寿命为碘 - 自由和碘化络合物分别发生。系间窜越到的最低三重态从纳秒到15-24 PS加速到200倍;其速率相关与在corrole的π系统的碘P（PI）参与和自旋 - 轨道耦合（SOC）的强度。 TDDFT计算具有明确SOC表明碘化介绍低洼单线的歧管和三重态碘 - ＆GT; corrole电荷转移（CT）的状态。这些状态影响通过提供用于索瑞松弛级联光物理（I） - ＆GT; q内部转换和冷却以及（ii）打开新的SOC的途径，由此三重态CT字符混入两个Q-单重激发态。此外，较高的Q单线态和三提高作为前沿corrole的π轨道的增加碘参与索瑞之间SOC。我们的观察，该发色团周边的碘化通过改变电子结构影响到整个光周期，自旋 - 轨道耦合，以及态密度理顺“重原子效应”和具有用于控制激发态动力学的影响的范围内三重态的光敏剂。

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