脯氨酸与Cu、Cu~+和Cu~(2+)配位体系的计算研究

运用M06-2X和ωB97XD方法分别在6-311++G(2d,p)和TZVP基组水平上,对脯氨酸(Pro)的15种构象与Cu、Cu+和Cu2+形成的多种配合物的几何结构、能量学特征、振动光谱和电子结构等进行计算研究.四种水平得到20种[Pro-Cu]、16种[Pro-Cu]+和16种[Pro-Cu]2+稳定结构.[Pro-Cu]和[Pro-Cu]+体系中出现12种Pro构象,而[Pro-Cu]2+体系中出现11种Pro构象,三种体系中最稳定的结构都不是由能量最低的Pro构象生成的.在结构CI3、CI4、CII7和CII8中,Pro的羧基氢转移到亚氨基氮形成两性离子与Cu双配位结合.[Pro-Cu]0/1+/2+体系四种水平计算相对能差范围逐渐增加,结合能分别在-60.0--5.0 kJ·mol-1、-340.0--170.0 kJ·mol-1和-1100.0--860.0 kJ·mol-1范围,配位体系中Pro的变形能逐渐增加.N―H和O―H键伸缩振动频率普遍发生红移,配位体系中部分电荷从Pro转移到Cu上,在[Pro-Cu]2+体系中单配位结构中电荷转移最多,约为单位负电荷.

Computational Study on the Coordinate Systems of Proline with Cu,Cu+ and Cu2+

The geometric and electronic structures, energetics, and vibrational frequencies of different coordinate systems formed between 15 conformers of proline (Pro) and Cu, Cu⁺, and Cu²⁺ were investigated in detail, using the M06-2X and ωB97XDmethods with 6-311++G(2d, p) and TZVPbasis sets.Atotal of 20, 16, and 16 stable [Pro-Cu]^0/1+/2+ complexes were obtained at four levels. These structures demonstrated that 12 conformers of Pro exist in the [Pro-Cu] and [Pro-Cu]⁺ systems, while 11 conformers are present in the [Pro-Cu]²⁺ complexes. The most stable complexes are evidently not formed by the lowest energy conformer of Pro with Cu, Cu⁺, and Cu²⁺. In the CI3, CI4, CII7, and CII8 complexes, the carboxyl group hydrogen of Pro was found to transfer to the imino nitrogen to forma zwitterion. Both the relative energy difference and the deformation energy of Pro gradually increase along with the charge number of the Cu. The binding energies of the [Pro-Cu]^0/1+/2+ systems were determined to be in the ranges of -60.0 to -5.0, -340.0 to -170.0, and -1100.0 to -860.0 kJ· mol^-1, respectively. The stretching vibrational frequencies of the N―H and O―H bonds in Pro all exhibit a general red shift on complexation. Additionally, each systemshows charge transfer fromthe Pro to the Cu, even in the case of [Pro-Cu]²⁺, some complexes that have more than one negative charge.