CREST/JST and Department of Physics, Graduated School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan.
J Phys Chem A. 2011 Mar 24;115(11):2110-9. doi: 10.1021/jp111313f. Epub 2011 Mar 1.
The photophysical properties of a carbonyl-containing carotenoid analogue in an s-cis configuration, relative to the conjugated π system, 2-(all-trans-retinylidene)-indan-1,3-dione (C20Ind), were investigated by femtosecond time-resolved spectroscopy in various solvents. The lifetime of the optically forbidden S(1) state of C20Ind becomes long as solvent polarity increases. This trend is completely opposite to the situation of S(1-ICT) dynamics of carbonyl-containing carotenoids, such as peridinin and fucoxanthin. Excitation energy dependence of the transient absorption measurements shows that the transient absorption spectra in nonpolar solvents were originated from two distinct transient species, while those in polar and protic solvents are due to a single transient species. By referring to the results of MNDO-PSDCI (modified neglect of differential overlap with partial single- and double-configuration interaction) calculations, we conclude: (1) in polar and protic solvents, the S(1) state is generated following excitation up to the S(2) state; (2) in nonpolar solvents, however, both the S(1) and the (1)nπ* states are generated; and (3) C20Ind does not generate the S(1-ICT) state, despite the fact that it has two conjugated carbonyl groups.
在不同溶剂中，通过飞秒时间分辨光谱研究了 s-cis 构象的含羰基类胡萝卜素类似物相对于共轭π体系 2-(全反式视黄醛基)-茚并-1,3-二酮（C20Ind）的光物理性质。C20Ind 的光禁态 S(1) 态的寿命随着溶剂极性的增加而延长。这种趋势与含羰基类胡萝卜素（如叶黄素和岩藻黄素）的 S(1-ICT)动力学完全相反。瞬态吸收测量的激发能依赖性表明，非极性溶剂中的瞬态吸收光谱源自两个不同的瞬态物种，而极性和质子性溶剂中的瞬态吸收光谱则归因于单个瞬态物种。通过参考 MNDO-PSDCI（带部分单重和双重组态相互作用的修正忽略微分重叠）计算的结果，我们得出结论：（1）在极性和质子性溶剂中，S(1)态是在激发到 S(2)态后生成的；（2）然而，在非极性溶剂中，S(1)态和（1）nπ*态都会生成；（3）尽管 C20Ind 有两个共轭羰基，但它不会生成 S(1-ICT)态。
