咪唑啉缓蚀剂分子结构与缓蚀性能的量子化学分析

Quantum chemical analysis on molecular structures and inhibitive properties of imidazoline inhibitors

采用量子化学密度泛函理论,考察6种十一烷基咪唑啉缓蚀剂的缓蚀性能与分子结构的关系,通过前线轨道分布、Fukui指数、自然电荷分布以及分子中重原子对前线轨道贡献等分析缓蚀剂分子的反应活性位点。结果表明:咪唑啉类缓蚀剂分子与金属界面作用时,主要是咪唑环和亲水支链上的极性基团起作用,分子的活性位点主要分布在咪唑环及亲水取代基上的N、O、S等杂原子处;缓蚀剂的缓蚀效率与分子最高占有轨道能量(EHOMO)、最低空轨道能量(ELUMO)及分子负电荷总数(nTNC)都有较好的相关性;咪唑啉缓蚀剂与金属相互作用时,既能向金属原子的空轨道提供电子形成配位键,又可从金属中接受电子到缓蚀剂分子最低空轨道上形成反馈键,从而形成稳定的吸附。

The relationships between molecular structures of six undecyl imidazoline inhibitors and their inhibitive performance were investigated by using quantum chemical density functional theory（DFT）.Via analysis of frontier orbital distribution,Fukui index,natural charge distribution and contribution to frontier orbital of heavy atoms,the reaction active sites of imidazoline molecules were obtained.The results indicate that imidazoline ring and its polar functional group on the hydrophilic chain play a significant role when inhibitors react with metal surface,and the reaction active sites mainly concentrate on the imidazoline ring and atoms of N,O,S located on hydrophilic substituent.The inhibition efficiency is closely related to some quantum chemical parameters of corrosion inhibitors such as the highest occupation orbital energy EHOMO,the lowest empty orbital energy ELUMO and total number of molecular negative charge nTNC.The imidazoline molecules could form coordinate bond and back-donating bond to metal surface when inhibitors react with metal,and stable adsorption could be formed.