A new palladium(II) complex with ibuprofen: Spectroscopic characterization, DFT studies, antibacterial activities and interaction with biomolecules

Abstract

This work describes the synthesis, characterization and antibacterial activities of a palladium(II) complex with ibuprofen (ibu). Elemental and mass spectrometric data (ESI-QTOF-MS) suggest a 1:2 metal/ligand composition with the minimal formula PdC26H34O4. Infrared (IR) and nuclear magnetic resonance (NMR) spectroscopic measurements indicate ligand coordination to palladium(II) by the carboxylate group in a bidentate mode. Thermal analysis shows that decomposition of the Pd-ibu complex starts at 130 °C and occurs in three exothermic stages. The steps are consistent with the loss of two ibuprofen molecules, with the formation of the final residue of the thermal treatment at 850 °C. DFT calculations (LANL2DZ basis set), supported by the spectroscopic data, led to an optimized dimeric structure for the complex, where two palladium(II) centers are interconnected by four carboxylates in a cage-like structure. The palladium(II) complex with ibuprofen (Pd-ibu) is soluble in dimethylsulfoxide (DMSO) and hexane and is slightly soluble in ethanol and acetonitrile. The complex exhibited antibacterial activities against Gram-positive (Staphylococcus aureus and Enterococcus faecalis) and Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacterial strains, which is noteworthy in the search of new antibacterial agents. Strong interactions were evidenced with biomolecules such as deoxyribonucleic acid (DNA) and bovine serum albumin (BSA) using agarose gel electrophoresis and fluorescence assays, respectively, which suggests that such molecules are possible targets for the complex in biological medium.