Examining the binding mechanism of 3,4-dihydro-3-(2-oxo-2-phenylethylidene)-quinoxalin-2(1H)-one and its fragments to Cu<sup>2+</sup>
作者:Efrat Korin、Beny Cohen、Yong-Dong Liu、Cheng-Chu Zeng、Alexander I. Shames、James Y. Becker
DOI:10.1080/00958972.2013.803535
日期:2013.7.1
The structure and stoichiometries of the complexes that could be formed between Cu2+ and 3,4-dihydro-3-(2-oxo-2-phenylethylidene)-quinoxalin-2(1H)-one (1) were investigated by various spectral techniques such as IR, fluorescence, UV-vis and electron paramagnetic resonance. The results suggest that initially 3:1 and 2:1 (1/Cu2+) complexes are formed at low Cu2+ concentration and upon adding more Cu2+, 1:1 (preferred) and 1:2 complexes are generated. Since 1 possesses two possible binding sites, further exploration was done by testing the binding ability of Cu2+ to fragments of 1, namely -enaminoketone derivatives (2-3) and quinoxaline-2-one (4), and by executing calculations of thermodynamic parameters of the reaction between 1 and Cu2+ in ethanol, optimized geometries of the possible complexes, and estimation of stability constants at various stoichiometries. Consequently, a step-by-step binding mechanism is suggested for formation of various complexes between 1 and Cu2+.