N-(2-羟基苯亚甲基)苯胺衍生物分子内质子转移取代基效应的密度泛函理论研究

Study on the Substituent Effect of Intramolecular Proton Transfer of N-(2-Hydroxybenzylidene) Aniline Derivatives by Density Functional Theory

在B3LYP/6-31+G(d,p)水平上研究了N-(2-羟基苯亚甲基)苯胺衍生物分子内质子转移的取代基效应.结果表明:吸电子基引入后会让分子更加趋于平面构型,而供电子基取代后让分子发生了一定程度的扭转;吸电子取代基引入后减小了分子平面的电子密度,拉近了N_1-H_2距离,增强了分子内氢键的强度,降低了醇式到酮式的结构互变能垒.供电子取代基引入后增加了分子平面的电子密度,加大了N_1-H_2间距,减弱了分子内氢键的强度,使得质子转移能垒升高.对分子的前沿轨道研究表明醇式较酮式结构来说更易形成激发态,并且能隙随着吸电子能力和供电子能力增强变小,说明其生物活性变强.

The substituent effect of intramolecular proton transfer of N- （2-hydroxybenzylidene ） aniline derivatives were studied at the B3LYP/6-31 ＋ G （d, p） level. The results show that the introduction of the electron withdrawing group make the molecules more tending to the planar configuration, and the electron donor replace the molecules to a certain degree of torsion. After the introduction of the electron- withdrawing substituents, the electron density of the molecular plane is reduced The N1 -H2distance enhances the intramolecular hydrogen bondstrength and reduces the structure of the alcohol to ketone. The electron recombination of the electron donor increases the electron density of the molecular plane, increases the Nt -H2 spacing, reduces the intensity of the intramolecular hydrogen bonds, and increases the proton transfer energy barrier. The study of the molecular prospective orbit shows that the alcohol is more likely to form an excited state than the ketone structure, and the energy gap decreases with the increase of the electron-withdrawing ability and the electron-supplying ability, which indicates that the biological activity becomes stronger.