八元瓜环超分子作用下2-(2-氨基-3-吡啶基)苯并咪唑的质子转移

摘要

利用荧光发射光谱、紫外吸收光谱和核磁共振氢谱(1H NMR)研究了八元瓜环(CB8)与2-(2-氨基-3-吡啶基)苯并咪唑(2-A3PyBI)的超分子相互作用及其对2-A3PyBI分子内质子转移过程的影响.结果表明,在水溶液中2-A3PyBI具有双重荧光发射峰,分别对应其2种质子转移异构体.固定pH值下的荧光滴定实验表明主客体包合比为1∶2,2-A3PyBI进入CB8空腔后促进了其分子内激发态质子转移过程.同时,1H NMR结果表明2-A3PyBI的苯环部分进入了CB8空腔.%The inclusion interaction of 2-(2-amino-3-pyridyl)-benzimidazole(2-A3PyBI) with cucurbit[8] uril(CB8) and the effect of the interaction on the proton transfer of 2-A3PyBI were studied via fluorescence emission spectroscopy, UV absorption spectroscopy and 1H NMR. The results show that 2-A3PyBI has a dual emission fluorescence which corresponds to its proton transfer tautomers. The fluorescence titration results at selected pH value indicate that the interaction ratio is 1 :2 and the encapsulation of 2-A3PyBI into CB8 cavity enhances the excited-state intramolecular proton transfer process. The 1H NMR titration results, which the benzene ring signal upward but no obviously change of the pyridine ring was observed in DC1/D2O, indicate that the benzene ring of 2-A3PyBI entrapped into the CB8 cavity with the pyridine ring outside the cavity.