Synthesis, Characterization, Antibacterial and Antifungal Activities Evaluation of Metal Complexes With Benzaldehyde-4-methylthiosemicarbazone Derivatives

Herein, to develop the comprehension of the microbiological activity of metal complexes based on benzaldehyde-N4-thiosemicarbazone derivatives, we described the synthesis, characterization of copper(II), zinc(II) and cadmium(II) complexes with vanillin-4-methylthiosemicarbazone (MTSVN) and 3,4-dihydroxybenzaldehyde-4-methylthiosemicarbazone (MTSDHB). The crystal structures of the [ZnCl2(MTSVN)2] (L1 C1) and [CdBr2(MTSDHB)2.H2O]2 (L2C5) complexes were determined by the single X-Ray diffraction method, the central ion is coordinated through the sulphur. For the other complexes, the ion is coordinated through the sulfur as well as azomethine nitrogen atom of the thiosemicarbazone. All these compounds, the two ligands and the new nine complexes were screened in vitro for their antifungal activity against human pathogenic fungi: Candida albicans and Aspergillus fumigatus, and for their antibacterial activity against Gram (+) bacteria such as Bacillus subtilis and Enterococcus faecalis as well as against Gram (−) bacteria such as Paracoccus yeei and Acinetobacter baumanii. By investigating the structure-activity relationships, we found that the two ligands MTSVN (L1) exhibited significant effect against E. faecalis and A. baumanii and the MTSDHB (L2) acted only against E. faecalis. Furthermore, all the complexes (L1C1–L1C4 and L2C1–L2C5) showed significant antifungal and antibacterial activities against gram-positive, gram-negative bacteria, and two fungal human pathogens.