Spectrophotometric method for studying the stability of late lanthanide complexes

The results of studying the effect of the central metal ion on the stability of gadolinium and holmium complexes with 1,10'-phenanthroline-2,9-dicarboxylic acid diamide are presented. The obtained values of the stability constants of the complexes turned out to be an order of magnitude lower than the previously known values for the complexes of these elements with 4,7-dichloro-1,10'-phenanthroline-2,9-dicarboxylic acid diamide.