Excited state properties of aryl carotenoids
Excited state properties of aryl carotenoids
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DOI：
10.1039/b921384h
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发表时间：
2010-01-01
影响因子：
3.3
通讯作者：
Polivka, Tomas
中科院分区：
文献类型：
--
作者：
Fuciman, Marcel;Chabera, Pavel;Polivka, Tomas
用飞秒瞬时吸收光谱研究了绿色硫磺细菌捕光触角的重要组成部分--芳基类胡萝卜素的激发态性质。为了探索共轭芳基的影响，我们研究了一系列含共轭phi环的芳基类胡萝卜素、绿细菌、β-异丁烯和异丁烯，并将它们与含有β-环的非芳基对应的g-胡萝卜素和β-胡萝卜素进行了比较。将β-环改变为Phi-环没有发现吸收光谱的任何变化，表明Phi-环对有效共轭长度的影响可以忽略不计。这一观察结果进一步得到了类胡萝卜素S-1寿命的支持。在正己烷中，一环绿细菌的S-1寿命为6.7ps，而β-环类似物g-胡萝卜素的S-1寿命为5.4ps。对S-1在正己烷中的寿命分别为8.2ps、10.3ps和12.7ps的β-胡萝卜素(两个β-环)、β-异丙三烯(一个β-环和一个斐环)和异桂烯(两个斐环)系列也观察到了同样的效应。芳基类胡萝卜素的系统较长的寿命表明，在phi-环上增加的共轭C=C键对共轭长度没有贡献。芳基类胡萝卜素在苯中的S1寿命略有缩短，表明苯环与苯间存在pi-pi堆积作用。
Excited-state properties of aryl carotenoids, important components of light harvesting antennae of green sulfur bacteria, have been studied by femtosecond transient absorption spectroscopy. To explore effects of the conjugated aryl group, we have studied a series of aryl carotenoids with conjugated phi-ring, chlorobactene, beta-isorenieratene and isorenieratene, and compared them with their non-aryl counterparts g-carotene and beta-carotene, which contain beta-ring. Changing beta-ring to phi-ring did not reveal any changes in absorption spectra, indicating negligible effect of the phi-ring on the effective conjugation length. This observation is further supported by the carotenoid S-1 lifetimes. In n-hexane, the S-1 lifetime of chlorobactene having one phi-ring is 6.7 ps, while the S-1 lifetime of the beta-ring analog, g-carotene is 5.4 ps. The same effect is observed for the series beta-carotene (two beta-rings), beta-isorenieratene (one beta- and one phi-ring) and isorenieratene (two phi-rings) whose S-1 lifetimes in n-hexane are 8.2, 10.3 and 12.7 ps, respectively. The systematically longer lifetimes of aryl carotenoids show that the additional conjugated C=C bonds at the phi-ring do not contribute to the conjugation length. The S1 lifetimes of aryl carotenoids were slightly shortened in benzene, indicating pi-pi stacking interaction between the phi-ring and benzene.