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采用CCSD/6-31++G**//B3LYP/6-31++G**方法研究了Cu2+诱导甘氨酸质子迁移的机理.优化得到了7个中性配合物和1个两性配合物,其中两性配合物最稳定,结合能为215.93 kcal mol-1.中性构型间通过分子内单键的旋转相互转化,C-N、C-C和C-O键旋转的能垒范围分别为1.62～2.49、0.27～7.80和2.27～16.97 kcal mol-1;中性构型N6经质子迁移变为两性构型,能垒为33.82 kcal mol-1.Cu2+作用于甘氨酸,使甘氨酸N5原子负电荷减少超过0.5,降低了N5对H6原子的库仑吸引,钝化了共价键B(O3–H6),动力学上不利于H6质子迁移;但是H6质子迁移后,形成的两性构型Z1却是热力学最稳定体系.
The mechanism of Cu2 + -induced glycine proton migration was investigated by CCSD / 6-31 ++ G ** // B3LYP / 6-31 ++ G ** method. Seven neutral complexes and one amphoteric complex were optimized, Among them, the amphoteric complexes were the most stable with a binding energy of 215.93 kcal mol-1. The neutral configurations were transformed by intramolecular single-bond rotation, and the energy barriers of CN, CC and CO bond rotation ranged from 1.62 to 2.49, 7.80 and 2.27 ~ 16.97 kcal mol-1, respectively. The neutral configuration N6 changed into the amphoteric configuration by proton transfer, with an energy barrier of 33.82 kcal mol-1.Cu2 + acts on glycine to reduce the negative charge of glycine N5 atom by more than 0.5, Coulomb attraction of N5 to H6 atom blunts the covalent bond B (O3-H6), which is not conducive to H6 proton transfer in kinetics. However, the formation of the zwitterionic configuration Z1 is the most thermodynamically stable system after H6 proton transfer.