Synthesis, in vitro evaluation of antibacterial, antifungal and larvicidal activities of pyrazole/pyridine based compounds and their nanocrystalline MS (M = Cu and Cd) derivatives

Abstract

Methyl 3,5-dimethyl pyrazole-1-dithioate (mdpa) (1), benzyl 3,5-dimethyl pyrazole-1-dithioate (bdpa) (2), 3,5-dimethylpyrazole-1-(5methyl-1H-pyrazol-3-ylmethyl)- 1H-pyrazole (3), copper(II)-mdpa (4), copper(II)-bdpa (5), cadmium(II)-mdpa (6), cadmium(II)-bdpa (7), Cu2S nanoparticles (8 and 9) derived from 4 and 5, respectively, CdS nanoparticles (10 and 11) derived from 6 and 7, respectively, were synthesized to screen their antimicrobial activities. Prolonged reaction with CuCl2.2H2O and 3 followed by addition of trace amount of pyridine furnished a crystalline chloro bridged complex [Cu(μ-Cl)2(pyridine)2]n and its structure was solved by single X-ray crystallography. Antibacterial activities of all of the synthesized materials (1–12) were evaluated against Gram positive bacteria including Staphylococcus aureus and Bacillus subtilis and Gram negative bacteria including Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae and Proteus vulgaris. Fungi (Candida albicans, Aspergillus flavus) were also used to test antifungal activities with the compounds. Present study revealed that 8 shows best antibacterial activity among the present reported compounds. An excellent antifugal activity is shown by 12 emerging to be a better antibiotic than standard fluconazole. Besides fungicidal effect, 12 has promising larvicidal effect. The structure and activity relationship has been discussed.