Synthesis, spectroscopic and thermodynamic studies of new transition metal complexes with N,N'-bis(2- hydroxynaphthalin-1-carbaldehydene)-1,2-bis(m- aminophenoxy)ethane and their determination by spectrophotometric methods

摘要

A novel tetradentate N_2O_2-type Schiff base, synthesized from 1,2-bis(m-aminophenoxy)ethane and 2-hydroxynaphthalin-1-carbaldehyde, forms stable complexes with transition metal ions such as Cu(II), VO(IV) and Zn(II) in DMF. Microanalytical data, elemental analysis, magnetic measurements, UV, visible and IR spectra as well as conductance measurements were used to confirm the structures. The stability constants of these complexes in 60 percent (v/v) DMF-water were determined at different ionic strengths (0.07,0.13,0.2 M) and at different temperatures (45, 50,55,60 +- 0.1 deg C) using a spectrophotometric method. From these constants, thermo-dynamic stability constants and thermodynamic parameters (DELTA G~0, DELTA H~0, DELTA S~0) were calculated. The values of enthalpy change are negative for all systems. The acid dissociation constant of the ligand, investigated in 60 percent (v/v) DMF-water, has also been calculated at different temperatures.