冠丙四肽与卤离子结合行为的理论研究

Theoretical study on the combination of halogen ion with crown tetraalanylpeptide

用密度泛函理论B3LYP方法,以环丙四肽的冠型构象(冠丙四肽)为模型基础,对氟、氯、溴等卤离子与其结合形式进行了几何构型优化、能量计算、Mulliken布局数分析等理论研究。结果表明冠丙四肽的构型在与卤离子结合前后几乎没有改变,结合过程中电子由卤离子移向冠肽,氟离子与冠型环丙四肽的结合作用明显优于氯离子和溴离子,卤离子的最佳结合位均略微偏离于模型中心轴线,此时氟、氯、溴离子距冠丙四肽中心的距离依次为0.084 nm、0.210 nm和0.200 nm。

The density functional theory based hybrid-method B3LYP was used to investigate the interaction of the halogen ions with crown tetraalanylpeptide which is the coronary structures of homodetic cyclotetraalapeptide and was represented as the model basic.Many properties including combination energy,optimum geometry structures and population analysis were calculated.It has been shown that there is scarcely any change in the coronary structure of C4-Ala after combination with X^-.The electrons move from halogen ions to C4-Ala during the combining process. Combination of C4-Ala with F- is obviously stronger than that of Cl- and Br-.When the energy of C4-Ala-X- is at minimum,the distances between halogen ions and the center of C4-Ala are 0.084 nm,0.210 nm and 0.200 nm,respectively.