新烟碱类化合物几何构型优化方法的选择

Selection of method for geometry optimization on neonicotinoid compounds

选用具有晶体结构实测数据的2种新烟碱类化合物吡虫啉和吡虫啉的N3位甲基取代物分子构型为基点,采用多种方法/基组对其结构进行优化。通过比较AM1、RHF/6-31G、RHF/6-31G(d)和B3LYP/6-31G、B3LYP/6-31G(d)等方法/基组优化得到的优势构型参数与试验所测定的晶体结构数据,并结合单点能、红外光谱特征峰值和优化所耗CPU时间等多个因素进行分析,结果表明:AM1、RHF/6-31G和B3LYP/6-31G 3种方法/基组优化2种目标化合物的所需CPU时间较短,但优化效果较差;RHF/6-31G(d)和B3LYP/6-31G(d)方法/基组所得结果均与晶体构型十分吻合,其中B3LYP/6-31G(d)方法所得结果最接近试验值,且2种化合物优化所需CPU时间比RHF/6-31G(d)法分别少31.1%和25.1%;3种方法相比较,B3LYP/6-31G(d)方法为新烟碱类化合物量子化学和定量构效关系研究最合适的方法。

Geometry optimization was carried out on neonicotinoid based on the crystal structure and molecular configuration of imidacloprid and the methyl substituent at N3 position of imidacloprid using a variety of methods and basis sets. Comparing the structural parameters obtained from calculation with the crystal structure data via AM1,RHF/6-31G, RHF/6-31G （d） and B3LYP/6-31G, B3LYP/6-31G（d） combined with the single-point energy, infrared spectroscopy and optimized CPU time, the result showed： the optimized CPU time of AM1, RHF/6-31G and B3LYP/6-31G were shorter, but the optimization was less effective; The optimization results of RHF/6-31G （d） and B3LYP/6-31G （d） were very consistent with the crystal conformation, among which the one obtained by B3LYP/6-31G was more accurate and consumed less CPU time than that obtained by RHF/6-31G （d）. Therefore, B3LYP/6-31G （d） was the most appropriate method for studying quantum chemical and QSAR of the neonicotinoid compound.