Synthesis and structures of 5-methoxy-salicylaldehyde thiosemicarbazonates of copper(II): Molecular spectroscopy, ESI-mass studies and antimicrobial activity

In this investigation, copper(II) complexes of 5-methoxy-salicylaldehyde-N1-substituted thiosemicarbazones {5-MeO-2-HOC6H4-C2(H)N3N2HC1(S)N1HR; R = Me, H2L-NMe; Et, H2L-NEt; Ph, H2L-NPh; H, H2L-NH2} with 2,9-dimethyl-1,10-phenanthroline (phen-2,9-Me2) and 3,4,7,8-tetramethyl-1,10-phenanthroline (phen-3,4,7,8-Me4) as co-ligands have been isolated. Complexes, namely, [Cu(κ3-O,N,S-L-NR)(κ2-N,N-L)] 1–8 (L = phen-2,9-Me2/phen-3,4,7,8-Me4) have been characterized by elemental analysis, infrared and electronic absorption spectroscopy, magnetic susceptibility measurements and single crystal X-ray crystallography. They have been studied for their fluorescence property, ESI mass study and antimicrobial activity against methicillin resistant Staphylococcus aureus (MRSA), Staphylococcus aureus (MTCC740), Klebsiella pneumoniae (MTCC109), Shigella flexneri (MTCC1457), Pseudomonas aeruginosa (MTCC741) and Candida albicans (MTCC227). Complexes, 1–8, have slightly distorted square pyramidal geometry and display intense fluorescence bands at λmax = 403–426 nm. ESI-mass spectral study has shown intense molecular ions [M+H]+. Copper(II) complexes have shown antimicrobial activity Complexes 5 and 6 with phenyl substitution at N1 nitrogen have shown enhanced antimicrobial activity with lowest minimum inhibitory concentration (MIC). The cellular toxicity against living cells was found to be high and thus these complexes are bactericidal/fungicidal.

The 5-methoxy-salicylaldehyde thiosemicarbazonates of copper(II) have slightly distorted square pyramidal geometry and have shown intense fluorescence. They have shown significant bactericidal/fungicidal effect against methicillin resistant Staphylococcus aureus (MRSA), Staphylococcus aureus, Shigella flexneri, Klebsiella pneumoniae, Pseudomonas aeruginosa and Candida albicans. The antimicrobial activity in general varies in the order: R = Ph > Et ∼ Me > H.Figure optionsDownload as PowerPoint slide