2-硫代黄嘌呤酸解离常数的量子化学理论研究  

Quantum chemistry theoretical investigation on the dissociation constant of 2-thioxanthine acid

作　　者：任宏江[1,2] 李小军[1] 

机构地区：[1]西北工业大学理学院应用化学系,陕西西安710072 [2]西安文理学院化学与化学工程学院,陕西西安710065

出　　处：《计算机与应用化学》2013年第5期553-556,共4页Computers and Applied Chemistry

基　　金：陕西省分析化学省级重点学科基金;西安市科技计划项目西安文理学院科研创新基金专项项目资助(CXY1134WL13)

摘　　要：采用密度泛函B3LYP方法在6-311+G^(**)级别上对2-硫代黄嘌呤气相和水相中较稳定的两个构型2TX(1,3,7)和2TX(1,3,9)及可能的8种离子构型进行了几何构型全优化和频率分析,水相优化选用IEFPCM模型,单点能计算采用CPCM溶剂模型并选取UAKS空穴方法。为了获得较精确的能量,在MP2/6-311+G^(**)级别下各物种分别在两相中进行了单点能计算。根据所计算的溶剂化吉布斯自由能进一步得到了水相4种相对稳定的离子异构体的pK_a值,理论计算结果与实验值基本一致,从而揭示了水溶剂中2-硫代黄嘌呤的电离活性部位和离子构型的存在形式。The geometrical structures of 2-thioxanthine two stable tautomers 2TX（1,3,7） and 2TX（1,3,9） as well as eight possible ionic forms were fully optimized in the gaseous and aqueous phases using Density Functional Theory B3LYP method at 6-311＋G＇＂ level. The IEFPCM model was employed for the geometry structure optimization in the aqueous phase. Single point energy calculations were carried out at MP2/6-311＋G＊＊ level combined with CPCM model for getting more accurate energies. The pKa values of five stable ionic tautomers were obtained in the base of the solvation Gibbs flee energy. The calculated results are in good agreement with that in the experiments, exploring the activity side and existing form of ionic tautomers for 2-thioxanthine in the aqueous phase.

关 键 词：2-硫代黄嘌呤 酸解离常数 密度泛函 IEFPCM模型 CPCM模型 

分 类 号：O641[理学—物理化学]