Excited state properties of peridinin: Observation of a solvent dependence of the lowest excited singlet state lifetime and spectral behavior unique among carotenoids
Excited state properties of peridinin: Observation of a solvent dependence of the lowest excited singlet state lifetime and spectral behavior unique among carotenoids
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DOI：
10.1021/jp9916135
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发表时间：
1999-10-14
影响因子：
3.3
通讯作者：
Frank, HA
中科院分区：
文献类型：
--
作者：
Bautista, JA;Connors, RE;Frank, HA
利用稳态吸收光谱、荧光光谱和瞬态光谱研究了多甲藻素在几种不同溶剂中的光谱性质和动力学行为。的最低激发单重态的多甲藻素的寿命被发现是强烈依赖于溶剂的极性和范围从7 ps的强极性溶剂三氟乙醇中的172 ps的非极性溶剂环己烷和苯。寿命与溶剂的极化率没有明显的相关性，溶剂分子与多甲苷的氢键不是决定最低激发单重态动力学行为的重要因素。最大发射波长、荧光量子产率和瞬态吸收光谱也受溶剂环境的影响。一个模型与数据一致，并支持初步的半经验计算调用的电荷转移状态的存在下，在激发态歧管的peridinin占的意见。电荷转移状态最有可能的结果从存在的内酯环的π-电子共轭的peridinin类似于以前的研究结果氨基香豆素和相关化合物。这里报道的行为是非常不寻常的多甲藻素类胡萝卜素，一般表现出很小的依赖性的光谱特性和最低激发单重态的溶剂环境的寿命。
The spectroscopic properties and dynamic behavior of peridinin in several different solvents were studied by steady-state absorption, fluorescence, and transient optical spectroscopy. The lifetime of the lowest excited singlet state of peridinin is found to be strongly dependent on solvent polarity and ranges from 7 ps in the strongly polar solvent trifluoroethanol to 172 ps in the nonpolar solvents cyclohexane and benzene. The lifetimes show no obvious correlation with solvent polarizability, and hydrogen bonding of the solvent molecules to peridinin is not an important factor in determining the dynamic behavior of the lowest excited singlet state. The wavelengths of emission maxima, the quantum yields of fluorescence, and the transient absorption spectra are also affected by the solvent environment. A model consistent with the data and supported by preliminary semiempirical calculations invokes the presence of a charge transfer state in the excited state manifold of peridinin to account for the observations. The charge transfer state most probably results from the presence of the lactone ring in the pi-electron conjugation of peridinin analogous to previous findings on aminocoumarins and related compounds. The behavior of peridinin reported here is highly unusual for carotenoids, which generally show little dependence of the spectral properties and lifetimes of the lowest excited singlet state on the solvent environment.