从头计算法研究沙蚕毒和杀虫环分子的几何构型与电子结构

Ab Initio Studies on Geometries and Electronic Properties of the Nereistoxin and Evisect

用Ｈａｒｔｒｅｅ－Ｆｏｃｋ／６－３１Ｇ从头算确定了沙蚕毒和杀虫环分子的几何构型，在全局优化中发现杀虫环分子的椅式和船式两种稳定构象，在二级Ｍｏｌｌｅｒ－ｐｌｅｓｓｅｔ微扰理论ＭＰ２／６－３１Ｇ水平下，椅式较船式稳定２７．０６ｋＪ／ｍｏｌ．用ＭＰ２／６－３１Ｇ波函数计算电子相关校正的分子静电势，以此为基础讨论生物活性与静电势的关系．发现对此二分子，Ｍｕｌｌｉｋｅｎ布居分析获得的原子净电荷存在问题，本文用Ｂｒｅｎｅｍａｎ提出的从静电势导出原子净电荷的ＣＨＥＬＰＧ方法计算了原子净电荷．

Ab initio calculations have been carried out at the Hartree-Fock/6-31G level to determine the geometries of the nereistoxin(C5H11NS2)and evisect(C5H11NS3).Two stable conformations of chair and boat forms of the evisect have been found in the global optimizations.At the second Moller-Plesset perturbation theory,MP2/6-31G level, the chair form is 27. 06 kJ/mol which is more stable than the boat form.The molecular electrostatic potentials obtained from MP2/6-31G wave-functions.The relationship between biological activity and electrostatic potentials have been discussed.The atomic charges from Mulliken population analysis is faulty in the nereistoxin and evisect.Brenneman's CHELPG method was used in the calculations.