用X3LYP杂化密度泛函方法在LACV3P**++基组水平上对脯氨酸(Pro)的15种构象与Ag原子和Ag+离子形成多种配合物的几何结构、电子结构、振转光谱和能量学特征进行了计算研究,结果得到17种Pro-Ag和23种Pro-Ag+稳定结构.数据分析表明:(1)Pro-Ag配合物中仅有Pro的9种构象出现,而Pro-Ag+配合物中则都涉及,最稳定结构并不是能量最低的Pro构象与Ag或Ag+生成:(2)Pro与4d105s1组态的Ag结合主要是范德华作用力,对Pro结构影响很小,配合物中存在较弱的特殊O-H…Ag氢键.外层5s5p全空的Ag+与配位原子间生成σ配位键.前者以单配位最稳定,后者以双配位最稳定;(3)Ag原子与Pro配位结合能小于-19 kJ·mol-1,而Ag+与Pro的结合能在-117--255 kJ·mol-1范围,形成热力学稳定体系Pro-Ag+;(4)自然键轨道(NBO)布局分析显示Pro-Ag和Pro-Ag+体系中Ag都获得少量负电荷,配合物的前线轨道能量差(△ε)均比两个碎片的低.配合物中O-H和N-H键的红移和蓝移都存在.%We calculated the geometrical and electronic structures, rotational and vibrational frequencies, and energetics of different complexes formed by 15 conformers of proline (Pro) with atomic and cationic Ag using the hybrid density functional method X3LYP and the LACV3P** ++ basis set together with effective core potentials.The Pro-Ag system gave 17 stable complexes and the Pro-Ag+ system gave 23 stable complexes.The results show that: (1) only 9 conformers of proline are present in the Pro-Ag complexes but all are present in the Pro-Ag+ complexes.The most stable complexes are not formed by the lowest energy conformer of proline with Ag and Ag+.(2) The main interaction between atomic Ag and proline is a van der Waals interaction because of its 4d105s1 electronic configuration.However, Ag+ binds strongly to proline with some σ-coordination bonding character due to the empty outermost 5s5p valence shell.Both particles can be mono- or bi-coordinate in complexes with proline.A non-conventional O-H…Ag hydrogen bond exists.(3) The binding energy between Ag and proline is less than -19 kJ·mol-1 but the binding energy of the Pro-Ag+ complex changed from -117 to -255 kJ·mol-1.The latter system was found to be more stable.(4) Ag carries a small amount of negative charge in two types of complexes according to natural bond orbital (NBO) population analysis and the energy differentce of front orbital values (Δε) of the complexes are lower than that of the Ag and proline fragments.The O-H and N-H bond stretching frequencies were found to be red shifted or blue shifted in some complexes.
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