Stereodifferentiation in the intramolecular singlet excited state quenching of hydroxybiphenyl–tryptophan dyads
作者:Paula Bonancía、Ignacio Vayá、Dimitra Markovitsi、Thomas Gustavsson、M. Consuelo Jiménez、Miguel A. Miranda
DOI:10.1039/c3ob27278h
日期:——
for coordination with water, as in the methyl ester (S)-BPOHMe or in the dyads, this effect was prevented; accordingly, the fluorescence quantum yields did not depend on the presence or absence of water. The fluorescence lifetimes in dry acetonitrile were 1.67, 0.95 and 0.46 ns for (S)-BPOH, (S,S)-1 and (S,R)-1, respectively, indicating that the observed quenching is indeed dynamic. In line with the steady-state
在(S,S)-1和(S,R)-1的非对映二体中发生的光化学过程。(S)-2-(2-羟基-1,1'-联苯-4-基)丙酸((小号) - BPOH)与(小号) -和(- [R )-色氨酸,进行了研究。在乙腈,(S,S)-1和(S,R)-1的荧光光谱在形状和位置上与(S)-BPOH一致,尽管它们显示出明显的立体选择性猝灭。由于禁止从BPOH到Trp的单线态能量转移(上坡5 kcal mol -1),因此淬灭归因于热力学上有利的(根据Rehm-Weller)电子转移或激基复合物形成。加上20%水,(S)-BPOH的荧光量子产率下降,而二元组仅观察到微小的变化。这可以通过(S)-BPOH的激发态酸度的增强来解释,这与羧基和羟基基团的桥接有关。水,并同意存在 水(S)-BPOH的X射线结构中的分子。当羧基不可用于配位时水,如在甲酯(S)-BPOHMe或二联体中一样,这种作用被阻止;因此,荧光量子产率不取