BDBPH——金属单核配合物的稳定性及其溶液中的形态分析

THE STABILITY OF MONONUCLEAR COMPLEXES OF BDBPH-METALS AND THE SPECIES DISTRIBUTION

目的 测定BDBPH—金属 (Zn、Mn、Cd)单核配合物的稳定常数 ,分析不同pH条件下各物种的存在形式及变化规律 ,比较BDBPH不同金属配合物的稳定常数的大小并讨论它们的影响因素。方法 温度2 5.0± 0 1℃、离子强度 0 .10 0mol L、N2 保护下用NaOH标准溶液滴定大环配体BDBPH—金属离子 (l:l)酸性溶液 ,滴定pH范围 2～ 12 ,高精度酸度计记录pH值 ,BEST程序计算稳定常数 ,SPE和SPEPLOT程序绘制样品分布曲线。结果 BDBPH—金属配合物的稳定常数分别为 17.72 (LogKZnL) ,11.58(LogKMnL) ,14.2 8(LogKCdL)。结论 配体BDBPH能够与金属离子 (Zn、Mn、Cd)形成稳定的单核配合物 。

Objective To Study the stability constants,and discuss the species distribution of the mononucleating complexes of BDBPH-metal. Methods The potentiometric equilibrium measurements were carried out with a Corning Model 350 digital pH meter under an atmosphere of Argon gas.The temperature was maintained at 25.0±0.l℃ and the ionic strength of the medium was maintained at 0.100mol/L.The stability constants were determined with the program BEST,and the species distribution diagram was obtained with the program SPE and SPEPLOT.Result The main stability constants are l7.72(LogK ZnL ),14 28(LogK CdL )11 58(LogK MnL ).Zn(Ⅱ)、 Cd(Ⅱ) and Mn(Ⅱ)do not combine with the ligand until the first two protons of the ligand have almost been completely neutralized.The main species was mononuclear complexes with the diprotonated ligand,MH 2L.The three metal ions also form mono-and noprotonated complexes,MHL,ML.The relative order of stailities of the mononuclear complexes,ML,is Zn(Ⅱ)>Cd(Ⅱ)>Mn(Ⅱ). Conclusion The ligand has strong tendency to form mononuclear complexes with Zn(Ⅱ)、 Cd(Ⅱ) and Mn(Ⅱ),as well as dinuclear complexes.