Synthesis and characterization of new copper(II) and palladium(II) complexes with azo-, bisazo-5-pyrazolones

New copper(II) and palladium(II) complexes were synthesized by the interaction of metal acetates and azo-, bisazo-5-pyrazolones in a methanolic medium. The mononuclear copper(II) and palladium(II) complexes were obtained from the ligands, HAP/HL1a–b and HAP/HL2 (Azo-5-Pyrazolone Ligand), and the binuclear copper(II) complexes were obtained from the ligands, HBAP/HL2a and HBAP/HL1c (BisAzo-5-Pyrazolone Ligand). The resulting complexes were characterized on the basis of spectroscopic techniques such as infrared, mass spectra, nuclear magnetic resonance and UV–visible absorption spectra as well as thermal analyses. The spectral data show that the ligands coordinated via the carbonyl oxygen of 5-pyrazolone and via the azo group of the nitrogen atoms of the azo-, bisazo-5-pyrazolones, except for the complex [Pd(HL1a)2] which coordinated from the carbonyl oxygen of 5-pyrazolone and the hydroxyl oxygen of the azo-substituted aromatic ring.