The complex stability constants of four bipyridine ligands with Eu(Ⅲ) in acetonitrile were determined by absorption spec-trophotometric titration. The four used bipyridine ligands are different with different para-substituents respectively:4,4′-dimethyl-2, 2′-bipyridine(DMBPY),4,4′-dihexyl-2,2′-bipyridine(DHBPY),4,4′-dinonyl-2,2′-bipyridine(DNBPY),and 2,2′-bipyridine-4, 4′-dimethylcarboxylate(DMABPY),In the experimental conditions,DMBPY,DHBPY and DNBPY form 1∶3 and 1∶2(M∶L)com-plexes with Eu(Ⅲ) ,but only 1∶3 complex formed for DMABPY. The NBO analysis of the complexes and the calculation of Gibbs free energy of the complexation reaction were performed with DFT method. The calculations conformed the experiment results and suggested that the difference of basicity of nitrogen because of the electro-property of the para-substituents is the reason for the de-crease trend of the stability constants of 1∶3 complexes:DHBPY>DMBPY>DMABPY.%采用吸收光谱法测定了在CH3CN溶剂中,4,4′-二甲基[2,2′]联吡啶、4,4′-二己基[2,2′]联吡啶、4,4′-二壬基[2,2′]联吡啶、[2,2′]联吡啶-4,4′-二羧酸甲酯等氮原子对位含不同电性能取代基的联吡啶与Eu(Ⅲ)的络合物稳定常数。在实验条件下,含烷基取代基(-CH3,-C6 H13,-C9 H19)的配体观察到1∶3和1∶2两种络合物,而含吸电基(-COOCH3)的仅观察到一种1∶3络合物。以1∶3络合物生成反应为模型反应,采用密度泛函方法计算了络合反应的自由能变化,证实不同电性能对位取代基对络合反应的影响,络合反应自由能变化与取代基的供电性强弱顺序相一致。
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