芳香性取代基对2-(2-羟基苯基)苯并咪唑激发态质子转移和光谱性质影响的理论研究  

Effect of aromatic substituent on the excited state proton transfer and spectral properties of 2-(2-hydroxyphenyl) benzimidazole:A theoretical study

作　　者：易平贵[1] 李玉茹 陶洪文[1] 彭文宇 梅刚 徐合意 YI Ping-Gui;LI Yu-Ru;TAO Hong-Wen;PENG Wen-Yu;MEI Gang;XU He-Yi(School of Chemistry and Chemical Engineering,Key Laboratory of Theoretical Organic Chemistry and Functional Molecules of Ministry of Education,Hunan Provincial Key Laboratory of Controllable Preparation and Functional Application of Fine Polymers,Hunan Province College Key Laboratory of QSAR/QSPR,Hunan University of Science and Technology,Xiangtan 411201,China)

机构地区：[1]湖南科技大学化学化工学院理论有机化学与功能分子教育部重点实验室精细聚合物可控制制备及功能应用湖南省重点实验室分子构效关系湖南省普通高校重点实验室,湘潭411201

出　　处：《原子与分子物理学报》2021年第1期1-8,共8页Journal of Atomic and Molecular Physics

基　　金：国家自然科学基金(21172066);湖南省教育厅重点科研项目(17A065)。

摘　　要：运用密度泛函(DFT)和含时密度泛函(TD DFT)理论方法研究了在2-(2-羟基苯基)苯并咪唑(HBI)苯环羟基的对位分别被呋喃基、吡咯基等五种芳香性取代基后的衍生物(HBI-R)分子内质子转移过程,考察了取代基的π电子离域效应对分子结构、分子内氢键和质子转移的影响,模拟计算了各分子的IR振动光谱和电子光谱.研究发现,基态的HBI与HBI-R分子内氢键O—H…N比O…H—N强度大,因氢键中的O—H增长和H—N的缩短,激发态氢键O—H…N弱于O…H—N强度,基态和激发态的稳定构型分别为醇式和酮式结构,取代基总体上使酮式构型相对稳定性有所增加,但呋喃基、吡咯基和噻吩基却略降低了激发态酮式构型相对稳定性.取代基降低了HBI基态和激发态分子内质子转移反应的能垒,但影响不大.电子吸收光谱的最大吸收峰和荧光光谱的最大发射峰主要源于前线分子轨道HOMO与LUMO之间的电子跃迁,芳环取代基增强了π电子离域效应,使光谱的吸收峰和发射峰波长均有较大的红移.The ground and excited state intramolecular proton transfer reactions of 2-(2-Hydroxyphenyl) benzothiazole(HBI) and its substituent derivatives(HBI-R) in the para position of hydroxyl in benzene ring with aromatic group,such as 2-furyl,2-pyrrolyl,2-thienyl,2-pyridinyl and phenyl,have been studied by using density functional theory(DFT) and time-dependent density functional theory(TD DFT) methods. The influences of πelectron delocalization effects of substituent groups on the molecular structures,intramolecular hydrogen bonds,proton transfer reactions have been explored. The IR vibration spectra and electron spectra of all molecules have been also simulated. The results show that for HBI and HBI-R molecules the strength of hydrogen bond O—H…N is stronger than O…H—N and the enol form is the stable tautomer in ground state,but O—H…N is weaker than O…H—N and keto form becomes lower in energy than enol in excited state owing to the increase of O—H length and decrease of N—H length in hydrogen bond. The stability of keto relative to enol tautomer is increased to some extent in general for HBI-R,except groups 2-furyl,2-pyrrolyl and 2-thienyl in excited state. Compared with HBI molecule,the energy barriers of proton transfer reaction for HBI-R are slightly decreased. The maximum absorption and emission peaks of each compound are all mainly ascribed to the electron transition between frontier molecular orbital HOMO and LUMO,and these peaks of HBI-R are red shifted greatly because of π electron delocalization effects of the aromatic substituent.

关 键 词：芳香性取代基 2-(2-羟基苯基)苯并咪唑 电子光谱 激发态分子内质子转移 密度泛函理论 

分 类 号：O641[理学—物理化学]