Synthesis and antimicrobial activities of Co (II), Ni (II) and Cu (II) complexes with N–S donor ligand

Aim

The extreme efforts have been developed to design novel compounds to strains of resistant micro-organisms. On-going search for novel and amazing drug delivery systems is primarily impact of the well-established fact that the convectional dosages are not sufficiently effective in conveying the drug compounds to its site of action and this has required the need to search for more efficient drugs. The metal complexes of Co (II), Ni (II) and Cu (II) with a tridentate ligand 2, 5-diamino-1, 3, 4-thiadiazole has been prepared by cyclisation of bithiourea in a 3% hydrogen peroxide medium. 2, 5-diamino-1, 3, 4-thiadiazole acts as neutral tridentate ligand and coordinates through the sulphur atom and nitrogen of the amines. The complexes are non-electrolyte in DMF. The complexes exhibited octahedral geometry. The antimicrobial activities of ligand and its complexes were screened using sensitivity test, minimum inhibition concentration and minimum bacterial concentration method. Metal chelates showed greater antimicrobial activities as compared to the control and the ligand. The metal chelates and the ligand did not exhibited activity against Aspergillus niger and Penicillin species.

Methods

Elemental analyses, IR spectra, magnetic susceptibilities by using Faraday Balance, molar conductance by using Genway 4200 conductivity meter. Metal estimation by using Alpha 4 Atomic Absorption Spectrophotometer. Thin layer chromatography was carried out using TLC plate coated with silica gel.

Results

The results of the elemental analyses are in good agreement with those calculated for the suggested formulae, 1:2 (M:L) solid chelates are isolated and found to have the general formulae [(ML2)] X2; M=Co (II), Ni (II) and Cu (II) (X=Cl). The IR spectra revealed that the ligand L is a neutral tridentate ligand. It coordinated to the metal ions via the nitrogen of the amines and sulphur atom. The molar conductance values of the Co (II), Ni (II), and Cu (II) complexes were relatively low, indicating the non-electrolytic nature of these complexes. The ligand and metal complexes show antimicrobial effect against the tested organism species except against molds of penicillin and Aspergillus. Niesseria gonorrhoea was probably the most sensitive organism to the 2, 5-Diamino-1, 3, 4-Thiadizole and its metal complexes. Metal complexes showed greater activity against some of the micro-organisms compared to the parent compounds.

Conclusion

In this paper we conclude from combined results of the chemical and physical analysis that the ligand (2, 5-diamino-1, 3, 4-thiadiazole) coordinated with Cu, Co and Ni. The metal complexes possess better physical properties than the parent compound. Metal complex of 2,5-diamino-1,3,4-thiadiazole would be a better therapeutic drug for antibacterial treatment.