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采用耦合簇量子化学方法 CCSD/aug-cc-pVDZ研究了嘧啶与嘌呤之间的相互作用,利用基函数叠加误差法(BSSE)消除相互作用能误差,并进行了几何结构优化;采用Gaussian 03程序包中的NBO程序分析了二阶稳定化能及自然键轨道.与此同时,应用约化密度函数(RDG)填色等值面图对体系进行了图形化分析,分析了氢键相互作用所在的空间位置和相对强度,以及氢键相互作用的性质,以进一步了解二者的相互作用.结果表明,嘧啶-嘌呤体系的相互作用属于闭合壳层静电相互作用.电子密度跃迁矩阵分析结果表明,激发区域主要集中在N原子和O原子处,涉及的空间广度很大,第一激发态主要涉及前线分子轨道,属于σ→π*或n→π*类型跃迁.
The interaction between pyrimidine and purine was studied by the coupled cluster quantum chemistry method CCSD / aug-cc-pVDZ. The error of interaction energy was eliminated by the base function superposition error method (BSSE), and the geometrical structure was optimized. The Gaussian 03 program The NBO program in the package analyzes the second-order stabilization energy and the orbital of natural bonds. At the same time, the system is graphically analyzed using the RDG color-fill isosurface map, and the interaction between hydrogen bonds The results show that the interaction between pyrimidine and purine belongs to the electrostatic interaction of closed shell.The results of electron density transition matrix show that the interaction between pyrimidine and purine belongs to the electrostatic interaction of closed shell, The excitation region is mainly concentrated at the N atom and the O atom, and the space involved is very wide. The first excited state mainly relates to the frontier molecular orbital and belongs to the type transition of σ → π * or n → π *.