Thermodynamic of Complexation of Lanthanides and Some Transition Metal Ions by 3,5-Dimitro-2'-Hydroxy Benzanilide

Abstract

The stepwise stability constants of (MHL) and (ML) complexes between transition (Cu²⁺, Ni²⁺, Co²⁺, Zn²⁺, Mn²⁺, Cd²⁺,) and lanthanide ions and 3,5-dinitro-2´-hydroxy benzanil (DHBH) in 75% (v/v) dioxane-water at constant ionic strength (0.01 M KNO₃) were determined at different temperatures. The thermodynamic
parameters for the proton-ligand and metal-ligand
stability constants were obtained by the temperature coefficient
method. The plot of thermodynamic parameters vs. ionic potential
(Z²/r) of the lanthanide elements is not linear as expected from ionic
theory. The obtained data support the interpretation of the expanded
solvation sphere through the lanthanide series. Anomalies in chelating
tendencies at gadolinium indicate a type of cross-over point at
which solvent-metal and ligand-metal interaction may occur.
Spectrophotometric studies were carried out for Cu²⁺-, Ni²⁺- and
Co²⁺-DHB complexes. The solid complexes were isolated and
characterized by elemental analysis, conductance, magnetic properties
and infra-red spectra.