四价锕系离子U(Ⅳ)和Th(Ⅳ)与肾上腺素配合物的研究

STUDY OF COMPLEXES FORMED BY ADRENALINE WITH U(Ⅳ) AND Th(Ⅳ)

本文采用电位滴定法和电子光谱法研究了肾上腺素及它与U(Ⅳ)和Th(Ⅳ)的溶液化学,探讨了各体系的平衡机理、配合物的组成、性质和稳定性.在t=25℃,I=0.10mol/1(KNO_3),氩气气氛中测得肾上腺素的各微观解离常数为:pk_1=8.74,pk_2=9.34,pk_(12)=9.80,pk_(21)=9.20;采用非线性最小二乘法BETA程序在CDC·CYBER170/825计算机上求得肾上腺素的宏观解离常数为pk_1~d=8.71,pk_2~d=9.83,pk_3~d=13.0和各配合物的形成常数为:lgβ_(UHL)=35.99,lgβ_(UL)=20.58,lgβ_(UH_2L_2)=45.17,lgβ_(UHL_2)=40.51,lgβ_(UL_2)=37.32;lgβ_(ThHL)=20.04,lgβ_(ThHL)=17.28,lgβ_(ThH_2L_2)=41.58,lgβ_(ThHL_2)=37.96,lgβ_(ThL_2)=32.49.

The solution chemistry of natural catechol derivative-adrenaline with actinides, U(Ⅳ) and Th(Ⅳ), have been investigated with pH-potentiometric titration and electronic spectroscopyin this work. The equilibrium mechanisms of various systems, composition, properties and stability of these complexes have been discussed. Microscopic dissociation constants of adrenaline are obtained by pH-spectrophotometric titrations at 25℃ ,0.1 mol/1 ionic strength(KNO3) and under argon atmosphere: pk1=8.74, pk2=9.34, pk12 = 9.80, pl21 = 9.20. It is explained with microscopic processes that the precipitate is .occurred at pH 9-10 and in the solution of more concentrated adrenaline. The macroscopic dissociation constants of adrenaline are given by pH-potentiometric titration under the same conditions: pKd1 = 8.71, pKd2=9.83, pKd3= 13.0. Absorption spectra of these complexes formed by the two metal ions with adrenaline are varied with pH within the range of λ = 250-350nm. It indicates that adrenaline coordinates with four valence actinides through the two oxygens of the phenolic groups. The coordination bonds of these complexes are chiefly possessed of ionicity, but the ionicity of U(??IV)-adrenaline complexes is relatively weak. The stability of U(Ⅳ) with adrenaline is stronger than that of Th (Ⅳ). The formation constants of these complexes are calculated using a non-linear least square program BETA to refine potentiometric titration data by CDC · CYBER 170/825 computer. They are as follows: lgβUHL =35.99, lgβUL =20.58, lgβUH2L2 =45.17, lgβUHL2 =40.51, lgβUL2 = 37.32; lgβThHl= 20.04, lgβThL = 17.28, lgβThH2L2 =41.58, lgβThHL2 =37.96, lgβThL2 =32.49.