Effect of carotenoid structure on excited-state dynamics of carbonyl carotenoids
Effect of carotenoid structure on excited-state dynamics of carbonyl carotenoids
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DOI：
10.1039/b909924g
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发表时间：
2009-01-01
影响因子：
3.3
通讯作者：
Polivka, Tomas
中科院分区：
文献类型：
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作者：
Chabera, Pavel;Fuciman, Marcel;Polivka, Tomas
利用飞秒时间分辨光谱技术研究了类胡萝卜素共轭体系中羰基的引入及其位置的影响。我们已经比较了四种具有可比结构的天然存在的类胡萝卜素，β-胡萝卜素，海胆酮，胡萝卜黄质和紫红质，它们在共轭羰基的数量和位置上不同。随着共轭C=O基团数量的增加，S-1的寿命系统性地变短，产生9.3 ps（β-胡萝卜素，无C=O基团），6.2 ps（海胆酮，一个C=O基团），4.5 ps（蓝黄质，两个C=O基团）和1.1 ps（紫红质，两个S-反式构型的C=O基团）。除了轻微的极性引起的吸收和瞬态吸收光谱的加宽，没有其他极性的影响，如缩短的S-1寿命或瞬态功能归因于分子内电荷转移（ICT）状态带，观察。这些极性诱导的功能的情况下被解释为由于长共轭链（无寿命缩短），和对称的羰基位置（无ICT带）。另一方面，所有的类胡萝卜素表现出的特征光谱带归因于S* 状态，并为两个最长的类胡萝卜素，黄质和紫红质，衰变的S* 状态是明显长于S-1状态。此外，它示出的S* 状态优先填充为基态构象的特定子集，强调类胡萝卜素构象在S* 状态形成的重要性。
Effects of introducing a carbonyl group and its position in the conjugated system of carotenoids were studied by means of femtosecond time-resolved spectroscopy. We have compared four naturally occurring carotenoids with comparable structures, beta-carotene, echinenone, canthaxanthin and rhodoxanthin, which differ in the number and position of conjugated carbonyl group(s). The S-1 lifetime is systematically shorter upon increasing the number of the conjugated C=O groups, yielding 9.3 ps (for beta-carotene, no C=O group), 6.2 ps (echinenone, one C=O group), 4.5 ps (canthaxanthin, two C=O groups), and 1.1 ps (rhodoxanthin, two C=O groups in s-trans configuration). Except for slight polarity-induced broadening of absorption and transient absorption spectra, no other polarity effects, such as shortening of the S-1 lifetimes or transient features attributable to intramolecular charge transfer (ICT) state bands, were observed. The absence of these polarity-induced features is explained as due to the long conjugated chain (no lifetime shortening), and the symmetrical position of the carbonyl groups (no ICT bands). On the other hand, all carotenoids exhibit the characteristic spectral band attributed to the S* state, and for the two longest carotenoids, canthaxanthin and rhodoxanthin, decay of the S* state is markedly longer than that of the S-1 state. Moreover, it is shown that the S* state is preferentially populated for a specific subset of ground state conformations, underlining the importance of carotenoid conformation in S* state formation.