2-(2,5-二羟基苯基)-4(3H)-喹唑啉酮质子转移及七元瓜环限制作用的理论研究

在B3LYP/6-311++G(d)和ONIOM(B3LYP/6-311++g(d):PM3)水平上,研究了2-(2,5-二羟基苯基)-4(3H)-喹唑啉酮(DHPQ)及其在七元瓜环(CB7)限制下的双质子转移过程,确定了DHPQ分子各互变异构体的结构、能量以及基态质子转移反应的过渡态.通过对结构变化和能量差异的分析,探讨了DHPQ中的双质子转移机理,考察了质子转移的纳米笼效应以及该笼效应对质子转移热力学性质的影响,同时研究纳米腔与DHPQ的几何匹配关系以及水溶剂对包合物质子转移的影响.计算结果表明:DHPQ是采取分步转移机理,纳米腔的限制对质子转移过程产生一个很大的能垒,抑制分子内质子转移过程,水溶剂的引入促进Path 2,抑制Path 1.

Theory study on intramolecular proton transfer for 2-(2,5-dihydroxyphenyl)-4(3H)-quinazolinone and restriction effect of cucurbit\[7\]uril

The ground-state intramolecular double proton transfer process of 2-(2,5-dihydroxyphenyl)-4(3H)-quinazolinone (DHPQ) and DHPQ@CB7 was studied systematically at the B3LYP/6-311++G(d) and ONIOM(B3LYP/6-311 ++G(d): PM3) levels. The structures and energies of all isomers for DHPQ and the transition states in the double proton transfer paths were determined. Through analysising the changes of structures and the differences of energy, the double proton transfer mechanism was explared existed in DHPQ, nanometer cage effect was considered on the thermodynamic properties in the process, at the same time, geometric matching relation between the nanocavity and DHPQ was studied as well as the effect of H2O medium on DHPQ proton transfer process. The results showed that double proton transfer process in DHPQ carried out step by step, the limit of nano cavity produced a large energy barrier, inhibiting the intramolecular proton transfer process, and the introduction of water solvent promoted the path 2 but inhibited path 1.