Transition Metal (II) Complexes with Nitrogen, Oxygen and Sulphur (NOS) Donor Schiff Base hydrazone: Synthesis, Spectroscopic and Antimicrobial Studies

Monobasic tridentate Schiff base hydrazone (pyrazine-2-carboxylic acid (phenyl-thiophen-2-yl-methylene)-hydrazide, HL) derived from condensation of pyrazine carboxylic acid hydrazide and 2-benzoyl thiophene reacted with transition metal (II) nitrates to form complexes of ML₂ type [where M = Mn(II), Co(II), Ni(II), Cu(II) and Zn(II)]. Schiff base hydrazone and metal complexes were characterized by spectroscopic techniques (IR, NMR, mass, electronic and ESR), molar conductance and room temperature magnetic successptibility measurements. On the basis of various physicochemical studies, octahedral geometry was proposed for Mn(II), Co(II), Ni(II), Zn(II) complexes and distorted octahedral geometry for Cu(II) complex. Schiff base hydrazone coordinated to metal ion through carbonyl oxygen, azomethine nitrogen and sulfur of thiophene ring. Schiff base and metal complexes have been evaluated for antimicrobial activities against various bacteria (Bacillus subtilis, Micrococcus luteus, Pseudomonas aeruginosa, Pseudomonas mendocina) and various fungi (Verticillum dahliae, Cladosporium herbarium, Trichophyton soudanense) at different concentrations i.e. 25, 50, 100, 200 μg/mL. The hydrazone ligand was found to be biologically active and a marked enrichment was observed in antimicrobial activity on coordination with metal ions.