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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Photophysics of Soret-excited tetrapyrroles in solution. I. Metalloporphyrins: MgTPP, ZnTPP, and CdTPP
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Photophysics of Soret-excited tetrapyrroles in solution. I. Metalloporphyrins: MgTPP, ZnTPP, and CdTPP

机译：溶液中Soret激发的四吡咯的光物理性质。 I.金属卟啉：MgTPP，ZnTPP和CdTPP

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The photophysical behavior of three Soret-excited diamagnetic meso-substituted tetraphenylmetalloporphyrins, MgTPP, ZnTPP, and CdTPP, have been examined in a wide variety of solvents using both steady-state and femtosecond fluorescence upconversion methods. The S-2 population of MgTPP decays to S-1 on the time scale of a few picoseconds with unit S-2-S-1 internal conversion efficiency, and the decay rates conform to the weak coupling case of radiationless transition theory. The energy gap law parameters characterizing the coupling of the S-2 and S-1 states of MgTPP have been obtained. The most important accepting vibrational modes in the S-1 state are multiple in-plane C-C and C-N stretches in the 1200-1500 cm(-1) range. Net S-2-S-1 decay is the dominant decay path for ZnTPP and CdTPP as well, but the process occurs at rates that exceed (in the case of CdTPP, they vastly exceed) those predicted by weak interstate coupling. Alternate mechanisms for the radiationless decay of the S-2 states of ZnTPP and CdTPP have been explored. Large spin-orbit coupling constants and the presence of multiple, near-equiergic triplet states suggest that S-2-T-n intersystem crossing might occur at rates competitive with internal conversion. However, the measured efficiencies of S-2-S-1 internal conversion show that, at most, only a few percent of the S-2 population of ZnTPP and no more than about 30% of the S-2 population of CdTPP can decay by a "dark" path such as intersystem crossing.
机译：已使用稳态和飞秒荧光上转换方法在多种溶剂中检测了三种Soret激发的反磁中观取代的四苯基金属卟啉MgTPP，ZnTPP和CdTPP的光物理行为。 MgTPP的S-2种群在几皮秒的时间尺度上以S-2-S-1单位的内部转换效率衰减到S-1，衰减速率符合无辐射过渡理论的弱耦合情况。已获得表征MgTPP的S-2和S-1状态耦合的能隙定律参数。在S-1状态下最重要的接受振动模式是在1200-1500 cm（-1）范围内的多个面内C-C和C-N拉伸。净S-2-S-1衰减也是ZnTPP和CdTPP的主要衰减路径，但是该过程的发生速率超过了弱的州际耦合所预测的速率（在CdTPP的情况下，它们大大超过了该速率）。已经探索了ZnTPP和CdTPP的S-2态无辐射衰减的替代机制。大的自旋轨道耦合常数和多个接近等当的三重态的存在表明，S-2-T-n系统间交叉可能以与内部转换竞争的速率发生。但是，测得的S-2-S-1内部转换效率表明，最多只有ZnTPP的S-2种群的百分之几和CdTPP的S-2种群的不超过约30％通过“暗”路径，例如系统间交叉。

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