Synthesis, crystal structure, and biological activity of 4′-chloro-2,2′ : 6′,2″-terpyridine (Cltpy) as tridentate ligand in a Cd(II) complex

Abstract

A new Cd(II) complex with 4′-chloro-2,2′ : 6′,2″-terpyridine (Cltpy), [Cd(Cltpy)(NO₃)₂(H₂O)_0.45(CH₃OH)_0.55], has been synthesized and characterized by CHN elemental analysis, ¹H-NMR, ¹³C-NMR, IR spectroscopy, and structurally analyzed by X-ray single-crystal diffraction. The single-crystal X-ray analyses show that the coordination number is seven with three terpyridine (Cltpy) N-donors, three oxygen atoms of two nitrates and one oxygen atom of methoxy/water. The antibacterial activities of Cltpy and its Cd(II) complex are tested against different bacteria. The free ligand has considerable activity against Staphylococcus aureus, Bacillus anthracis, and Pseudomonas aeruginosa (inhibition zones ≥ 20 mm), but has moderate activity against Escherichia coli and Streptococcus pyogenes (inhibition zones ≤ 15 mm). In comparison with free Cltpy ligand, its complex has more activity against Klebsiella pneumonia, S. aureus, and B. anthracis (inhibition zones ≥ 30 mm), but is inactive against P. aeruginosa and S. pyogenes. The quantitative assays gave minimal inhibitory concentration values in the range 6.25–100 mg mL⁻¹ that confirmed the above results. Against K. pneumonia and S. aureus, antibacterial activity of the complex is higher than Cltpy ligand.

Keywords:

• Cd(II) complex; 4′-Chloro-2,2′ : 6′,2″-terpyridine (Cltpy)
• Synthesis
• Crystal structure
• Antibacterial properties

Acknowledgments

This work was supported by the Payame Noor University, Khoy in Iran and Facultad de Quimica, Universidade de Vigo, 36310 Vigo Pontevedra in Spain.