s-四嗪-水簇复合物的理论研究

用量子化学B3LYP方法和6-31＋＋G**基函数研究了s-四嗪-水簇复合物基态分子间相互作用, 并进行了构型优化和频率计算, 分别得到无虚频稳定的s-四嗪-(水)₂复合物、s-四嗪-(水)₃复合物和s-四嗪-(水)₄复合物6个、9个和12个. 复合物存在较强的氢键作用, 复合物结构中形成一个N…H—O氢键并终止于O…H—C氢键的氢键水链构型最稳定. 经基组重叠误差和零点振动能校正后, 最稳定的1∶2, 1∶3和1∶4(摩尔比)复合物的结合能分别是41.35, 70.9和 94.61 kJ/mol. 振动分析显示氢键的形成使复合物中水分子H—O键对称伸缩振动频率减小(红移). 研究表明N…H键越短, N…H—O键角越接近直线, 稳定化能越大, 氢键作用越强. 同时, 用含时密度泛函理论方法在TD-B3LYP/6-31＋＋G**水平计算了s-四嗪单体及其氢键复合物的第一¹(n, p*)激发态的垂直激发能.

Theoretical Study of s-Tetrazine-(H2O)n (n=2,3,and 4)Cluster Complexes

The s-tetrazine-water (T-W) interactions have been investigated by examining the van der Waals clusters TW_n (n＝2, 3 and 4) using the density functional theory B3LYP method and the 6-31＋＋G** basis, obtaining 6, 9 and 12 minima of the ground state for the TW₂, TW₃ and TW₄ clusters respectively. The fully optimized ge-ometries and binding energies DE² were reported, including corrections of the basis set superposition error and zero point energies for the various stationary points. The global minima of the TW₂, TW₃ and TW₄ clusters have a hydrogen bond N…H—O and a chain of water molecules, terminated by a hydrogen bond O…H—C. The corresponding binding energies are 41.35, 70.9 and 94.61 kJ/mol, respectively, after the basis set superposition error and zero-point corrections. The H—O symmetric stretching modes of water in complex is red-shifted relative to that of the monomer water. In ad-dition, the shorter the bond length of N…H, the angle of N…H—O is closer to 180°, the stronger the hydro-gen bond interaction. The first singlet (n, p*) vertical excitation energy 2.227 eV of the monomer s-tetrazine and the T-W_n clusters have been investigated by time-dependent density functional theory.