Thermal, Spectroscopic and Antimicrobial Properties of Novel Nickel(II) Complexes with Sulfanilamide and Sulfamerazine Drugs

Synthesis and characterisation of metal-based Sulfa drugs have gained much attention in the past few decades, owing to their enhanced therapeutic applications. The present work aims to synthesise novel complexes of Nickel(II) with Sulfanilamide and Sulfamerazine, to prepare new metallodrugs with potential biological activities. The synthesis involves microwave irradiation method that provides a greener way for the synthesis of metallodrugs. Elemental, spectral and thermogravimetric analysis has been carried out to decipher the structural and coordination properties of drug molecules with the metal ion and to interpret the thermal Stability and decomposition behaviour of the complexes. Finally, the microbiological investigations have been done to explore the antibacterial activities of newly formed complexes. The study has been conducted at the Green Chemistry Research Centre, Govt. Dungar College, Bikaner and Ceramic Electrical Research and Development Centre, Bikaner. Effective metal drug coordination was confirmed by marked shifts observed in the UV/VIS spectrum of the complexes with respect to the parent drugs. FT-IR spectral studies revealed that sulfanilamide molecule coordinated to the metal ion only through its sulfonamidic nitrogen, whereas sulfamerazine molecule exhibited identity, chelating through its pyrimidic and sulfonamidic nitrogen atoms. Practically unaffected IR bands corresponding to the ligand SO2 group ruled out any possibility of coordination through O atom. Thermal stability of the complexes was determined through thermogravimetric (TGA) and differential thermogravimetric analysis (DTA). Important thermodynamic and kinetic parameters for their decomposition reactions were hence evaluated using Coats and Redfern integral equation. Antibacterial activities for both the complexes and pure drugs were screened against E. coli, S. aureus and B. subtilis. Whereas the efficacy of sulfamerazine is substantially enhanced upon metallation, the sulfamerazine complex showed diminished antibacterial properties as compared to its parent drug.