Synthesis and characterization of a series of novel metal complexes of N-heterocyclic azo-colorants derived from 4-azo-pyrazol-5-one

A series of novel metal complexes of Cu(II), Co(II), Ni(II), and Zn(II) with three N-heterocyclic derivatives of 4-azo-pyrazol-5-one were isolated and identified by FT IR, 1H NMR, ESR, and UV–Vis spectroscopy. The crystallographic data for a sodium salt as well as Co(II) and Cu(II) complexes were obtained. Formation constants of the complexes in ethanol aqueous solutions were calculated. Structures of yet unstudied metal complexes were proposed based on quantum-chemical modeling at the DFT/B3LYP level. © 2016 Elsevier Ltd