Excited state properties of beta-carotene analogs incorporating a lactone ring
Excited state properties of beta-carotene analogs incorporating a lactone ring
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掺入内酯环的 β-胡萝卜素类似物的激发态特性
DOI：
10.1039/c6cp06828f
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
H. Hashimoto
中科院分区：
文献类型：
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作者：
D. Kosumi;T. Kajikawa;K. Sakaguchi;S. Katsumura;H. Hashimoto
沿着其多烯主链具有羰基的类胡萝卜素由于在激发态发生分子内电荷转移（ICT）而表现出独特的激发态性质。事实上，天然存在的羰基类胡萝卜素的ICT特性在水生光合天线系统中进行的高效能量转移中起着至关重要的作用。在本研究中，我们合成了两个短链多烯类胡萝卜素纳入内酯环，表示为BL-7和BL-8，有7个和8个共轭双键（n = 7和8），分别。将这些化合物的激发态性质与它们的非羰基对应物的激发态性质直接进行比较，以澄清羰基在ICT生成中的作用。发现BL-7和BL-8的光学允许S2态的能量比非羰基短β-胡萝卜素同系物低0.3 eV（2400 cm−1）以上。超快光谱数据表明各种溶剂极性诱导的影响，包括在近红外区域的情况下的BL-7的受激发射的外观，和显着的寿命缩短的最低的单重S1激发态的BL-7和BL-8。这些结果表明，这些化合物表现出ICT特性。
Carotenoids possessing a carbonyl group along their polyene backbone exhibit unique excited state properties due to the occurrence of intramolecular charge transfer (ICT) in the excited state. In fact, the ICT characteristics of naturally occurring carbonyl carotenoids play an essential role in the highly efficient energy transfer that proceeds in aquatic photosynthetic antenna systems. In the present study, we synthesized two short-chain polyene carotenoids incorporating a lactone ring, denoted as BL-7 and BL-8, having seven and eight conjugated double bonds (n = 7 and 8), respectively. The excited state properties of these compounds were directly compared to those of their non-carbonyl counterparts to clarify the role of the carbonyl group in the generation of ICT. The energies of the optically allowed S2 states for BL-7 and BL-8 were found to be more than 0.3 eV (2400 cm−1) below those of non-carbonyl short β-carotene homologs. Ultrafast spectroscopic data demonstrated various solvent polarity-induced effects, including the appearance of stimulated emission in the near-IR region in the case of BL-7, and significant lifetime shortening of the lowest-lying singlet S1 excited states of both BL-7 and BL-8. These results suggest that these compounds exhibit ICT characteristics.