Antioxidant and Antibacterial Screening and Hg(II) Sensing, Activities of Cu(II)pyridine-2,6-dicarboxylate Complexes

In this study five different complexes of Cu(II) were synthesized for the purpose of environmentally notorious mercury sensing and preliminary biological screening. Pyridine-2,6-dicarboxylic acid (also known as dipicolinic acid, and abbreviated as H₂DPA), 3-phenyl pyrazole (3-ppz), 4-iodo-1H-pyrazole (4-ipz), 4-nitropyrazole (4-npz), 4-bromopyrazole (4-bpz), and 4-chloropyrazole (4-cpz) were chosen as potential ligands. The synthesized complexes labelled as 1–5, namely [Cu(DPA)(3-ppz)], [Cu(DPA)(4-ipz)], [Cu(DPA)(4-npz)], [Cu(DPA)(4-bpz)], [Cu(DPA)(4-cpz)], were proposed based on spectroscopic data (FTIR, TGA, and UV-visible spectroscopy). These complexes feature C=O functionalities that are not involved in coordination and may be used for further applications. The isolated complexes were utilized for detecting Hg(II) ions in water samples. Various concentrations of Hg(II) ions were prepared for detection purposes, and changes in absorption concerning complexes 1–5 were determined using UV-Visible spectroscopy. It was found that complexes 3 and 4 exhibit efficient sensing abilities towards Hg(II) ions. The antibacterial activities of complexes 1–5 were assessed against S. typhi and E. coli. The complexes 1 and 3 displayed good antibacterial activities against S. typhi (13.67, and 13.56 mm, respectively) while complexes 1, 2 and 4 were found to be efficient against E. coli (11.6, 12.66, 11.31 mm, respectively). The absorption maxima of 2,2-diphenyl-1-picryhydrazyl (DPPH) at 517 nm, considerably shifted upon addition of complexes 1–5. The results reveal that the complexes possess potential free radical scavenging abilities.