Applied studies of heterocyclic substituted azomethine-based chelator and its divalent complexes: synthesis, spectral and theoretical characterization

Abstract

An azomethine chelator (AC) obtained via condensation of 2-amino-6-nitrobenzothiazole and 2-hydroxy-1-naphthaldehyde was used to formulate M2+ complexes. The chelator, and its M2+ complexes were characterized using analytical and spectral techniques. AC acquired a yellow solid nature with 77.7% yield and a melting point of 278-280oC. The M2+ complexes had different shades, excellent yields and distinct melting points from 206oC. The latter exhibited solubility in dimethylformamide (DMF) and dimethylsurphoxide (DMSO). The infrared spectrum (IR) of AC showed an imine(H-C=N-) band around 1633 cm-1 while its M2+ complexes had their imine functional group bands between 1616-1642 cm-1. M-N and M-O bonds justifying coordination had their absorption bands appear between 647-513 and 580-457 cm-1 respectively. The electronic data of uncoordinated AC, displayed 4-bands at 254, 308, 342 and 398 nm, associated with л→л* and ո→π* transitions. Additionally, the M2+ complexes showed metal-ligand transition absorptions (428-822 nm) assigned to d→d shifts. The corrosion inhibitory investigation of AC at 100, 300 and 500 ppm in 1M-HCl, proved that when the concentration increased, the rate of corrosion consequently decreased while the efficiency of inhibition increased. The presence of S, O2 and H-C=N, may have aided this activity. In-vitro antibacterial screening in DMSO against S. aureus, B. cerus, P. aeruginosa, P. mirabilis, S. typhi and K. pneumoniae using streptomycin as positive control, presented activities in the range 1.0 – 14.0 mm. A. niger, A.s flaus, and R. stalonfer were used for antifungal evaluation using miconazole as standard drug. The inhibitions were recorded in the range 1.0–25.0 mm. These results prove that the compounds as promising antibacterial/antifungal drug pro-agents.