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采用B3LYP/6-31++G(d,p)方法研究Ni~(2+)催化甘氨酸质子迁移机理.优化得到了7个中性配合物和1个两性配合物;两性的最稳定,结合能为-927.3 k J/mol.分子内单键旋转和羧基H在2个羧基O原子间的迁移导致中性构型转化,C-C键旋转的能垒低于21.9 k J/mol,C-O键旋转的能垒在23.1-46.4 k J/mol范围内,羧基H在O原子间迁移的正逆反应能垒分别为175.0和108.3 k J/mol.羧基H迁移到氨基生成两性构型,能垒为19.3k J/mol.Ni~(2+)导致氨基N原子负电荷减少0.48,削弱了N原子对羧基H原子的库仑吸引,钝化了共价键B_(O3–H6),动力学上不利于羧基H迁移;但是羧基H迁移后,形成的两性构型却是热力学最稳定体系.最稳定中性构型N1转化为最稳定两性构型Z1的路径为:N1→N1-N7→N7→N3-N7→N3→N3-N5→N5→N5-Z1→Z1,该路径的最高能垒为124.8 k J/mol.
The B3LYP / 6-31 ++ G (d, p) method was used to study the catalytic mechanism of Ni 2+ for glycine proton transfer. Seven neutral complexes and one amphoteric complex were optimized. The most stable and binding Can be -927.3 kJ / mol. The intramolecular single bond rotation and the carboxyl group H transfer between the two carboxyl O atoms lead to the transformation of the neutral configuration. The energy barrier of the CC bond rotation is lower than 21.9 kJ / mol and the CO bond rotation Of the energy barrier in the range of 23.1-46.4 kJ / mol, the forward and reverse energy barrier of the carboxyl H in the migration of O atoms were 175.0 and 108.3 kJ / mol respectively.Carboxy H migration to the amino to generate amphoteric configuration, the energy barrier is 19.3 k J / mol.Ni ~ (2+) leads to a decrease of 0.48 in the negative charge of amino nitrogen atom, weakening the Coulomb attraction of N atom to carboxyl H atom, inactivating the covalent bond B_ (O3-H6) However, the amphoteric structure formed by the migration of carboxyl group H is the most thermodynamically stable system.The path from the most stable neutral configuration N1 to the most stable amphoteric configuration Z1 is: N1 → N1-N7 → N7 → N3 N7 → N3 → N3 → N5 → N5 → N5 → Z1 → Z1. The maximum energy barrier of this path is 124.8 kJ / mol.