Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA.
J Chem Phys. 2010 Aug 28;133(8):084303. doi: 10.1063/1.3466923.
Negative ions of copper-aspartic acid Cu(Asp)(-) and its hydrated complexes have been produced in the gas phase and studied by anion photoelectron spectroscopy. The vertical detachment energies (VDE) of Cu(Asp)(-) and Cu(Asp)(-)(H(2)O)(1,2) were determined to be 1.6, 1.95, and 2.20 eV, respectively. The spectral profiles of Cu(Asp)(-)(H(2)O)(1) and Cu(Asp)(-)(H(2)O)(2) closely resembled that of Cu(Asp)(-), indicating that hydration had not changed the structure of Cu(Asp)(-) significantly. The successive shifts to higher electron binding energies by the spectra of the hydrated species provided measures of their stepwise solvation energies. Density functional calculations were performed on anionic Cu(Asp)(-) and on its corresponding neutral. The agreement between the calculated and measured VDE values implied that the structure of the Cu(Asp)(-) complex originated with a zwitterionic form of aspartic acid in which a copper atom had inserted into the N-H bond.
铜-天冬氨酸的负离子 Cu(Asp)(-)及其水合配合物已在气相中产生，并通过阴离子光电子能谱进行了研究。Cu(Asp)(-)和 Cu(Asp)(-)(H(2)O)(1,2)的垂直离解能 (VDE) 分别确定为 1.6、1.95 和 2.20 eV。Cu(Asp)(-)(H(2)O)(1)和 Cu(Asp)(-)(H(2)O)(2)的光谱轮廓与 Cu(Asp)(-)非常相似，表明水合作用并未显著改变 Cu(Asp)(-)的结构。水合物种的光谱相继向更高的电子结合能移动，提供了它们逐步溶剂化能的测量值。对阴离子 Cu(Asp)(-)及其相应的中性体进行了密度泛函计算。计算出的和测量出的 VDE 值之间的一致性表明，Cu(Asp)(-)配合物的结构源于天冬氨酸的两性离子形式，其中一个铜原子插入了 N-H 键。
