间二氮杂苯-水簇复合物氢键结构与性质

Hydrogen Bbonding Structure and Property of Pyrimidine-water Clusters

用密度泛函理论在B3LYP/6-31++G**水平上对间二氮杂苯与水形成1:1,1:2和1:3复合物的氢键结构进行几何优化和性质计算,结果表明复合物之间存在较强的氢键作用。所有稳定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。氢键的形成使复合物中水分子H-O键振动频率减小(红移)。NBO分析表明,最稳定的1:1,1:2和1:3复合物发生分子间电荷转移总量分别为0.0266 e,0.03298 e和0.03786 e。同时,用含时密度泛函理论方法在TD-B3LYP/6-31++G**水平计算了间二氮杂苯单体及其氢键复合物的第一1(n,π*)激发态的垂直激发能。

Density functional theory B3LYP and 6-31＋＋G^＊＊ basis are employed to obtain the optimized geometries of the ground states for several Pyrimidine-（H2O）n （n=1,2,3） complexes. All calculations indicate that the pyrimidine-water complexes in the ground states have strong hydrogen bonding interaction, and the structure having a N…H-O hydrogen bond and a chain of water molecules, which is terminated by a O…H-C hydrogen bond is most stable. The H-O stretching modes of water in complex is red-shifted relative to that of monomer water. In addition, the NBO analysis indicates that intermolecule charge transfer is 0.026 6e, 0.032 98 e and 0.03786 e for the most stable 1：1, 1：2 and 1：3 complexes between pyrimidine and water, respectively. The first singlet （n,π^＊） vertical excitation energy of the monomer pyrimidine and the hydrogen bonding complexes between pyrimidine and water have been investigated by time-dependent density function theory.