Two-pump-one-probe femtosecond studies of Ni(II) porphyrins excited states.
Two-pump-one-probe femtosecond studies of Ni(II) porphyrins excited states.
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Ni(II) 卟啉激发态的双泵一探针飞秒研究。
DOI：
10.1021/ja0448059
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发表时间：
2004
影响因子：
15
通讯作者：
Rodgers,MichaelAJ
中科院分区：
文献类型：
--
作者：
Zamyatin,AndreyV;Gusev,AlexV;Rodgers,MichaelAJ
用双泵-单探针瞬态吸收光谱法研究了meso-四（4-磺酸基苯基）卟啉镍（NiTPPS）和meso-四苯基卟啉镍（NiTPP）的双激发态.双激发态是指在金属卟啉的两个不同区域中吸收两个光子以产生电子激发的分子态的分子实体。400和550 nm的两个连续脉冲用于激发。第一个脉冲（400 nm）产生卟啉π-系统的S2态，其失活产生S1态，随后产生金属中心（d，d）态。第二（550 nm）脉冲选择性地靶向具有激发金属中心的那些分子的S 0 → S1跃迁，并且在第一激发事件之后约40 ps被递送到样品。此时，四吡咯π-体系的基态已经再生，激发位于金属中心。在DMSO中的NiTPPS瞬变的动力学曲线显示双指数衰减，时间常数为0.6和4 ps。光激发的NiTPP在甲苯和NiTPPS在水中导致类似的行为。提出了一种涉及形成分子内电荷转移态的Ni（II）卟啉双激发态失活机理。
Dual excited states of nickel(II)meso-tetra(4-sulfonatophenyl)porphyrin (NiTPPS) and nickel(II)meso-tetraphenylporphyrin (NiTPP) have been investigated by two-pump−one-probe transient absorption spectrometry. By dual excited states, we mean molecular entities that have absorbed two photons to generate molecular states with electronic excitation in two distinct regions of metalloporphyrin. Two successive pulses of 400 and 550 nm were used for excitation. The first pulse (400 nm) produced an S2state of the porphyrin π-system, which deactivated to give rise to an S1state and subsequently produce a metal-centered (d,d) state. The second (550 nm) pulse selectively targeted an S0→ S1transition of those molecules having an excited metal center and was delivered to the sample approximately 40 ps after the first excitation event. At this time, the ground state of the tetrapyrrole π-system was already regenerated and the excitation was localized at the metal center. The kinetic profiles of the NiTPPS transients in DMSO revealed biexponential decays with time constants of 0.6 and 4 ps. Photoexcitation of NiTPP in toluene and NiTPPS in water resulted in similar behavior. A mechanism for the Ni(II) porphyrin dual excited state deactivation involving the formation of an intramolecular charge transfer state has been proposed.