锌(Ⅱ)-甘氨酸-水三元配合物结构和性质的理论研究

Theoretical study on structure and properties of ternary complexes[Zn(Gly_m)(H_2O)_n]^(2+)

采用CCSD//M06/6-31++G**理论方法系统研究了三元配合物[Zn(Gly_m)(H_2O)_n]^(2+)的结构和性质.气相模型下得到的结果为:(1)1个O,O双啮型两性甘氨酸分子比1个N,O双啮型中性甘氨酸分子的配位能力强9.7kJ·mol^(-1),比2个水分子强55.0kJ·mol^(-1);(2)O,O双啮型两性甘氨酸优先与Zn^(2+)配位,结合能为-810.4kJ·mol^(-1);增加的前2个水分子与Zn^(2+)直接配位最稳定;第3个水分子则插入到甘氨酸O原子和Zn^(2+)之间得到最稳定结构;然后第4和第5个水分子继续和Zn^(2+)配位.液相模型下的构型结构与气相结果近似,能量次序与气相结果相同.

A CCSD//M06/6-31＋＋G＊＊ method was used to systematically investigate the structure and properties of ternary complexes [Zn（Glym）（H2O）n]^2＋.The results obtained under the gas-phase model are as follows：（1）Coordination ability of the zwitterion glycine molecule（coordination sites are two O atoms）is stronger by 9.7 kJ·mol^-1 than that of the neutral glycine molecule（coordination sites are the N and O atoms）,and is stronger by 55.0 kJ·mol^-1 than that of two water molecules.（2）The bidentate glycine with O,O coordination sites preferentially coordinates with Zn^2＋,and the binding energy is -810.4 kJ·mol^-1.Direct coordination of the first two increased water molecules and Zn2＋ is the most stable.However,when the third water molecule is inserted between the O atom of glycine and Zn^2＋,the resulting structure is the most stable.Then the fourth and fifth water molecules continue to coordinate with Zn2＋.The structure of each conformation of liquid-phase model is similar to that of the gas-phase,and the energy order is also the same.