Synthesis, characterization, thermodynamic and thermal studies of Zn(II) complexes with di-2-pyridyl ketone salicyloylhydrazone

This paper shows the characteristics of a coordinated compound formed by zinc(11) and di-2-pyridyl ketone salicyloylhydrazone (DPKSH). The synthesized complex shows the formula: Zn(DPKSH)(2). Elemental analysis, electron ionization and electrospray mass spectra indicated the 1:2 metal/ligand molar ratio. The IR spectra show that DPKSH is coordinated to zinc(II) through the oxygen from the enolic or the phenolic group as the nuCO frequency was suppressed and the nuCO (phenolic) band was shifted to higher frequency in the IR spectrum of the complex. Two other interactions can be attributed to the nitrogens from the azo and the pyridine groups. Thermal decomposition and differential scanning calorimetry (DSC) are different for the ligand and the complex. The overall formation constants were obtained in ethanolic solution 50% (V/V), at pH 4.5 and 25 degreesC, resulting in beta(1) = 1.07 x 10(5) and beta(2) = 1.05 x 10(10). The molar absorptivies of the 1: 1 (epsilon(1)) and 1:2 0;2) complexes (Zn(11):DPKSH) were found to be 1.1 x 10(4) and 4.5 x 10(4) (M(-1)cm(-1)), respectively. (C) 2004 Elsevier Ltd. All rights reserved.