Spectroscopic investigation of peridinin analogues having different pi-electron conjugated chain lengths: exploring the nature of the intramolecular charge transfer state.
Spectroscopic investigation of peridinin analogues having different pi-electron conjugated chain lengths: exploring the nature of the intramolecular charge transfer state.
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DOI：
10.1021/jp903923r
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发表时间：
2009-10-15
期刊：
影响因子：
--
通讯作者：
Frank HA
中科院分区：
文献类型：
--
作者：
Niedzwiedzki DM;Chatterjee N;Enriquez MM;Kajikawa T;Hasegawa S;Katsumura S;Frank HA
据报道，多甲素和许多其他含羰基的类胡萝卜素和多烯的最低激发单线态 (S1) 态的寿命取决于溶剂的极性。这种效应归因于这些分子的多种激发态中存在分子内电荷转移（ICT）态。这种信息通信技术国家的性质尚未阐明。在目前的工作中，我们对具有不同数量的共轭碳-碳双键的多甲素和三种合成类似物C33-多甲素、C35-多甲素和C39-多甲素进行了稳态和超快时间分辨光谱分析。否则，这些分子在结构上相似，因为它们具有相同的官能团。该系统系列分子的稳态和瞬态光谱分布位置的趋势允许将光谱特征分配给涉及 S0、S1、S2 和 ICT 状态的转变。动力学分析揭示了激发态的寿命及其激发态失活途径的动力学。数据中最引人注目的观察结果是，对于所有多甲素类似物，无论 π 电子共轭程度如何，ICT 状态的寿命在极性溶剂甲醇中都收敛到相同的值 10.0 ± 2.0 ps。这表明 ICT 态高度集中在内酯环上，这是所有分子的共同结构特征。数据进一步表明，S1 和 ICT 状态的行为独立，ICT 状态由 S1 和 S2 填充，S1 的速率和效率取决于类胡萝卜素 π 电子链的长度和溶剂极性。
The lifetime of the lowest excited singlet (S1) state of peridinin and many other carbonyl-containing carotenoids and polyenes has been reported depend on the polarity of the solvent. This effect has been attributed to the presence of an intramolecular charge transfer (ICT) state in the manifold of excited states for these molecules. The nature of this ICT state has yet to be elucidated. In the present work, steady-state and ultrafast time-resolved optical spectroscopy have been performed on peridinin and three synthetic analogues, C33-peridinin, C35-peridinin, and C39-peridinin which have different numbers of conjugated carbon-carbon double bonds. Otherwise, the molecules are structurally similar in that they posses the same functional groups. The trends in the positions of the steady-state and transient spectral profiles for this systematic series of molecules allow an assignment of the spectral features to transitions involving the S0, S1, S2 and ICT states. A kinetics analysis reveals the lifetimes of the excited states and the dynamics of their excited state deactivation pathways. The most striking observation in the data is that the lifetime of the ICT state converges to the same value of 10.0 ± 2.0 ps in the polar solvent, methanol, for all the peridinin analogues regardless of the extent of π-electron conjugation. This suggests that the ICT state is highly localized on the lactone ring which is a common structural feature in all the molecules. The data further suggest that the S1 and ICT states behave independently and that the ICT state is populated both from both S1 and S2, the rate and efficiency from S1 being dependent on the length of the π-electron chain of the carotenoid and the solvent polarity.
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