Synthesis, spectral, thermal and thermodynamic studies of oxovanadium(IV) complexes of Schiff bases derived from 3,4-diaminobenzoic acid with salicylaldehyde derivatives

Synthesis and evaluation of three new oxovanadium(IV) complexes, formed by the interaction of vanadyl acetylacetonate and the Schiff bases: 3,4-bis((E)-2-hydroxybenzylideneamino)benzoic acid (L-1), 3,4-bis((E)-2-hydroxy-3-methoxybenzylideneamino)benzoic acid (L-2) and 3,4-bis((E)-2,4-dihydroxybenzylideneamino)benzoic acid (L-3) in methanol. The complexes have been characterized and studied by IR spectra, UV-Vis spectroscopy and thermogravimetry in order to evaluate their thermal stability and thermal decomposition. According to the results discussed from TG curves, the order of thermal stability for the complexes is VOL3 > VOL1 > VOL2. Their formation constants (K-f) were obtained by UV-Vis spectroscopic titration at 15, 25, 35 and 45 degrees C in methanol by SQUAD software. The trend of formation constants of the complexes as follows: VOL3 > VOL2 > VOL1. (C) 2013 Elsevier B.V. All rights reserved.