Synthesis, Spectral Characterization, Electrochemical, Antioxidant and Antimicrobial Evaluation of 3d-Metal Complexes of 3-Mercapto-4-(Pyren-1-ylmethylene)Amino-1,2,4-Triazin-5-One

Abstract

New transition metal complexes of cobalt(II), nickel(II), copper(II) and zinc(II) with new Schiff base [HL^p] derived from pyrene-1-carbaldehyde and 4-Amino-3-mercapto-5-oxo-1,2,4-triazine were synthesized and characterized by elemental analysis, ¹H-NMR, FT-IR, UV-Visible, ESR spectral studies, magnetic moment measurements and cyclic voltammetry. Results prove that [HL^p] acts as bidentate ligand. Low conductance data reveal non-electrolytic nature of the complexes. The spectroscopic data and magnetic moment values along with elemental analytical data support octahedral geometries for Co(II), Ni(II), Zn(II) complexes and square planar geometry for Cu(II) complexes. ESR spectra of Cu(II) complexes exhibited g values trend as $g_{\parallel }>g_{\perp }> g_e.$ The nephelauxetic ratio (β) along with orbital reduction factors (K values) report the covalent nature of the metal-ligand bonds in complexes. Thermal analysis was also carried out to propose the composition of complexes and to determine their thermal stability. Coats-Redfern method was employed to evaluate some kinetic parameters of thermal degradation processes. In vitro antimicrobial properties of all synthesized compounds were investigated. After assessing the inhibition zones, metal complexes have been found more antimicrobial active than the Schiff base against both bacterial as well as fungal strains. Metal complexes also showed remarkable fluorescence and antioxidant properties.

Keywords:

• Antimicrobial metal complexes
• bidentate Schiff base
• fluorescent complexes
• 3-mercapto-4-(pyren-1-ylmethylene)amino-1,2,4-triazin-5-one
• thermogravimetric analysis
• antioxidant activity

Acknowledgments

The authors express genuine gratefulness to DST-FIST programme 2017 and Department of Chemistry, Kurukshetra University Kurukshetra for providing necessary research facilities.

Disclosure statement

No potential conflict of interest was reported by the author(s).