Studies in influence of ionic strength of medium on the complex equilibria of substituted hydoxy-1-3-propandiones with Cr(III) and La(III) metal ions pH metrically

The solution studies (the proton-ligand stability constant pK and metal-ligand stability constants log k) of binary (1 : 1) complexes of Cr(III) and La(III) with 1(2'-Hydroxy-5'-Bromophenyl)-3- (4'-chlorophenyl)-1,3-Propanedione [HB4CP] [L1] and 1(2'-Hydroxy-5'-Bromophenyl), 3-(4'- Aminophenyl)-1,3-Propanedione [HB4AP] [L2] have been performed at 0.02 to 0.1 mol.dm-3 ionic strength at (29 ± 0.1)°C in 70 % dioxane-water mixture pH-metrically. The pk and log k values are utilized to estimate the thermodynamic stability constants at zero ionic strength and to know the exact nature of complexation equilibria.