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Spectral, NLO and antimicrobial studies of Co(II), Ni(II) and Cu(II) complexes of Schiff base ligands of 2-amino-6-nitrobenzothiazole

Kanagavalli Chinnaraj (Theni college of Arts and Science, Department of Chemistry, Veerapandi, Theni, Tamil Nadu, India)
Sankarganesh Murugesan (Mohamed Sathak Engineering College, Chemistry Research Centre, Kilakarai, Ramanathapuram, Tamil Nadu, India)
Dhaveethu Raja Jeyaraj (Mohamed Sathak Engineering College, Chemistry Research Centre, Kilakarai, Ramanathapuram, Tamil Nadu, India)
Kalanithi Manivannan (Jayaraj Annapackium College for Women, PG and Research Centre of Chemistry, Periyakulam, Theni, Tamil Nadu, India)

Novel series of Co(II), Ni(II) and Cu(II) transition metal complexes were synthesized from the Schiff base ligands HL1–HL4 derived from 2-amino-6- nitrobenzothiazole with various aromatic aldehydes, i.e., 4-methylbenzaldehyde, 4- ethylbenzaldehyde, 2-hydroxybenzaldehyde and 4-hydroxybenzaldehyde, respectively. The ligands HL1–HL4 and their metal (II) complexes were characterized by atomic absorption spectroscopy (AAS), magnetic susceptibility and molar conductance measurements, and UV–Vis, FT-IR and NMR spectroscopic techniques. The spectroscopic studies revealed that the complexes of HL1–HL3 coordinated in an octahedral environment and L4 in square planar/tetrahedral geometry. The ligands HL1–HL4 and their metal(II) complexes were screened for their antimicrobial activities against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Candida albicans. The results suggest that the complexes of HL4 possess greater inhibition activity towards C. albicans. The nonlinear optics (NLO) activities of ligands HL1–HL4 were determined. The obtained results showed that ligands HL1 and HL2 have greater second harmonic generation (SHG) efficiency than HL3and HL4.

Keywords: aldehydes, metal(II) complexes, spectroscopic, AAS, biological activity