Synthesis, Characterization, Antimicrobial Activity and Antioxidant Studies of Metal (II) Complexes of Schiff Base Derived from 2 – Hydroxy - 1- Naphthaldehyde and Hydrazine Monohydrate

Abstract

Transition metal complexes of Co(II) and Ni(II) with Schiff base ligand (HL) derived from condensation of 2- hydroxy-1-naphthaldehyde and hydrazine monohydrate were successfully synthesized and separated. The Schiff base ligand and the metal (II) complexes prepared were characterized by melting point/decomposition temperature, solubility, conductivity, FT-IR spectra and elemental analysis results. IR spectra of the free ligand showed a band at 1655cm^-1 which is assigned to the (-C=N-) stretching vibration of the azomethine. This band was observed at lower frequencies in the spectra of the metal (II) complexes which indicate complexation. Low (5.00 – 7.00Ohm^-1cm²mol^-1) conductivity measurement obtained showed that the complexes are non electrolyte while elemental analysis result revealed 1:1 Metal-Schiff base ratio. The in vitro antimicrobial assay showed that the compounds are active against most of the bacterial isolates (E. coli, Kleb pneumonia, P. mirabilis, P. aeruginosa, and S. aureus) as well as fungal isolates (C. albicans, F. solani, A. and fumigates). Antioxidant activity of the phenolic Schiff base against 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radicals was ascertained by employing probit analytical method using SPSS 16.0 software. The IC₅₀ for the phenolic Schiff base revealed its promising use as an antioxidant.

Keywords: Antioxidant, Complex, DPPH, Schiff base, 2-hydroxy-1-naphthaldehyde