Solvent-Sensitive Sign Inversion of Excimer Origin Circularly Polarized Luminescence in Bipyrenyl Peptides
Solvent-Sensitive Sign Inversion of Excimer Origin Circularly Polarized Luminescence in Bipyrenyl Peptides
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DOI：
10.1002/slct.201701315
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发表时间：
2017-09-11
期刊：
影响因子：
2.1
通讯作者：
Imai, Yoshitane
中科院分区：
文献类型：
--
作者：
Mimura, Yuki;Kitamura, Sayaka;Imai, Yoshitane
利用圆偏振发光（CPL）和圆二色性（CD）光谱研究了带有两个芘基的对映体纯寡肽（DD-2/LL-2：两个芘基之间有四个亚甲基间隔基; DD-1/LL-1：没有亚甲基间隔基）在8种常用有机溶剂（CHCl 3，CH 2 Cl 2，MeOH，CH 3 CN，DMF，NMP，DMAc和丙酮）中的光激发和基态手性.有人发现，手性的芘源CPL和CD信号的迹象在很大程度上取决于溶剂的性质，并容易受到亚甲基间隔。实际上，DD-1/LL-1在DMF中在450-510 nm处的准分子源CPL符号分别为（-）/（+），而在其它溶剂中的准分子源CPL符号分别为（+）/（-）。另一方面，在DD-2/LL-2中，在CH 2Cl 2（和CHCl 3）中，准分子来源的CPL符号分别为（-）/（+），在MeOH/DMF/NMP/DMAc中分别为（+）/（-）。同时发现DD-1/LL-1和DD-2/LL-2的CD符号反转依赖于溶剂和亚甲基间隔基，这表明溶剂和亚甲基间隔基共同影响着体系的基态手性和光激发手性.
The photoexcited and ground state chiralities of enantiopure oligopeptides bearing two pyrenyl groups (DD-2/LL-2: four methylene spacer between two pyrenyl groups and DD-1/LL-1: no methylene spacer thereof) in eight common organic solvents (CHCl3, CH2Cl2, MeOH, CH3CN, DMF, NMP, DMAc, and acetone) were investigated by means of circularly polarized luminescence (CPL) and circular dichroism (CD) spectroscopies. It was found that chiroptical signs of pyrene-origin CPL and CD signals largely depend on the nature of solvents and are susceptible to the methylene spacer. Actually, the excimer-origin CPL signs at 450-510 nm of DD-1/LL-1 in DMF were (-)/(+), respectively, while those in other solvents were oppositely (+)/(-), respectively. On the other hand, in DD-2/LL-2, the excimer-origin CPL signs were (-)/(+) in CH2Cl2 (and CHCl3), respectively, and (+)/(-) in MeOH/DMF/NMP/DMAc, respectively. The solvent dependent and the methylene spacer dependent CD sign inversion of DD-1/LL-1 and DD-2/LL-2 were also found. These results led to conclude that the solvent molecule and the methylene spacer collaboratively affect both the ground state chirality and the photoexcited chirality.