Spectroscopic studies on 2-[2-(4-methylquinolin-2-yl)hydrazono]-1,2-diphenylethanone molecule and its metal complexes

The electronic absorption spectra of a hydrazone: 2-[2-(4-methylquinolin-2-yl)hydrazono]-1,2-diphenylethanone (BHQ) derived from 2-hydrazino-4-methylquinoline and 1,2-diphenylethan-1,2-dione (benzil) have been studied in various solvents of different polarities. The dependence of the band shift Δύ on the solvent parameters viz. D, Z, E_T, DN, AN, α, β and π* was discussed. Also, the effect of pH on the free hydrazone and its Co(II), Ni(II) and Cu(II) complexes was studied spectrophotometrically in 75% (v/v) dioxane–water in order to determine the dissociation and stability constants. The stoichiometry of the formed complexes was determined by three different methods: Job's, mole ratio and slope ratio which indicate the formation of 1:2, M:L complexes for Co(II) and Cu(II) and 1:1, Ni(II):L. Beer's law is valid in the range 0.32–7.04 μg/mL depending on the type of the metal ion. The use of BHQ as an indicator via a spectrophotometric titration of Cu(II) and Ni(II) with EDTA was efficient.