Synthesis of diazole-thiols derivatives from l-cysteine: Characterization, complex formation with Ni(II), Cu(II) and evaluation of their antibacterial activity

Four novel diazole-thiol derivatives namely: 5-(1-amino-2-sulfanylethyl)-1,3,4-oxadiazole-2(3H)-thione 6, 4-amino-5-(1-amino-2-sulfanylethyl)-4H-1,2,4-triazole-3-thiol 7, 1-amino-3-(1-amino-2-sulfanylethyl)-1H-1,2,4-triazole-5-thiol 8, and 5-(1-amino-2-sulfanylethyl)-1H-1,2,4-triazole-3-thiol 9 have been synthesized from l-Cysteine and characterized by IR, 1H NMR, 13C NMR and GC–MS. Complex formation with Ni(II) and Cu(II) ions with four diazole-thiol derivatives of l-Cysteine were formed and isolated. The final synthetic products (6–9) and their corresponding Ni(II) and Cu(II) complexes (6a,a′-9a,a′) were tested against Gram-negative bacteria: Escherichia coli, Pseudomonas aeroginosae and Gram-positive bacteria: Staphylococus aureus 25923 and showed no biological activity. While Ni(II) and Cu(II) complexes of 7–9 exhibited appreciable activity against tested microorganisms. The outstanding results is that the Cu(II)-complexes 8a′ and 9a′ showed their (MIC) activity on similar organisms at very low concentrations (5 µg/ml) which is in fact lower concentration than what had been reported on other relative compounds.