Complex formation of rare earths with some bidentate Schiff bases: A thermodynamic study

Proton-ligand stability constants of 1-(4'-methylphenyl)-2-methyl-2-(2'-hyd roxy-5'-bromophenyl)imine (R-1), 1-(4'-nitrophenyl)-2-methyl-2-(2'-hydroxy- 5'-bromophenyl)imine (R-2) and 1-(2'-chloro-5'-nitrophenyl)-2-methyl-2-(2'- hydroxy-5'-bromophenyl)imine (R-3) and formation constants of their metal chelates with trivalent La, Cc, Pr, Nd, Sm, Gd, Tb, Dy, Yb and Ho have been determined at 25, 35 and 45 degrees and mu = 0.1 M(NaClO4) in 50 : 50 etha nol-water medium by Irving-Rossotti method. The log K-II and log K values a re used to discuss the effect of substituent and the atomic size of the rar e earth elements. The thermodynamic parameters for the formation of 1 : 1 a nd 1 : 2 complexes have been calculated.