溶液中N-乙酸基取代氮氧杂大环及其配合物稳定性研究

用pH电位滴定法在25℃,0.5mol·L~(-1)KNO_3水溶液中测定了三种大环化合物:H_2L~1(1,12-二氮杂-3,4:9,10-二苯并-5,8-二氧杂环十五烷-N,N＇-二乙酸);H_3L~2(1,12,15-三氮杂-3,4:9,10-二苯并-5,8-二氧杂环十七烷-N,N＇,N″-三乙酸)和H_2L~3(1,15-二氮杂-3,4:12,13-二苯并-5,8,11-三氧杂环十八烷-N,N′-二乙酸)的逐级质子化常数.又测定了它们与Cu~(2+)、Ni~(2+)、Pb~(2+)配合物的稳定常数,以及H_2L~3与镧系金属La~(3+)、Pr~(3+)、Nd~(3+)、Eu~(3+)、Sm~(3+)、Gd~(3+)、Dy~(3+)、Yb~(3+)配合物的稳定常数.讨论了三种大环化合物质子化的一般顺序及其与各种离子配位时稳定性选择规律.说明了影响配位稳定性的有关因素.

STUDY OF N-FUNCTIONATIZED OXYGEN-NITROGEN DONOR MACROCYCLES AND THE STABILITY OF THEIR COMPLEXES IN SOLUTION

The protonation constants of three macrocyclcs: 1,12-diaza- 3,4:9,10- dibenzo- 5,8-dioxacyclopentadecane-N,N'-diacetic acid (H2L1); l,12,15-triaza-3,4:9,10-dibenzo-5,8-dioxacycloheptadecane-N,N',N" -triacetic acid (H3L2) and 1,15- diaza -3,4:12,13-dibenzo-5,8,11- trioxacyclooctadccanc -N,N'- diacetic acid (H2L3) were determined by potentiometric titrations. The stability constants of the complexes of H2L1, H3L2, H2L3 with Cu2+, Ni2+, Pb2+ and the complexes of H2L3+ with La3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Dy3+, Yb3+ were determined by the same method. A FORTRAN program BEST was revised for computation of all the constants from potentiometric titration data. The general process of protonation of donor atoms for the three ligands were discussed. The complcxation selectivity rules of these ligands with mctalions were documented and the factors affecting the stability of these complexes were proposed based on the experiment results.