Zinc(II) complexes derived from imidazo[1,2-a]pyridin-2-ylacetic acid (HIP-2-ac): [Zn(IP-2-ac)₂(H₂O)] and unexpectedly, [Zn₃(IP-2-ac)₆(H₂O)]·11H₂O

Abstract

Two zinc(II) complexes based on imidazo[1,2-a]pyridin-2-ylacetate (IP-2-ac), [Zn(IP-2-ac)₂(H₂O)] (1) and [Zn₃(IP-2-ac)₆(H₂O)]·11H₂O (2), were synthesized and characterized by single-crystal X-ray diffraction. In both 1 and 2, zinc(II) ions are five-coordinate with N₂O₃ donor set, best described as a distorted trigonal-bipyramidal geometry. In 1, two IP-2-ac ligands chelate zinc(II) through a N,O donor set, whereas in 2, both bidentate and μ-bridging binding modes of IP-2-ac are observed. The crystal of 1 comprises discrete Zn(IP-2-ac)₂(H₂O) coordination entities combined into layers by hydrogen bonds. Inter-layer stabilization of the 3-D crystal lattice is provided by weak C–H⋯O contacts and π⋯π interactions. The structure of 2 consists of discrete trinuclear Zn₃(IP-2-ac)₆(H₂O) coordination entities joined into crystal lattice by multiple water molecules.

Compound 1 was characterized by FTIR and FT-Raman spectroscopy, and in terms of thermal stability. Furthermore, its antibacterial activity was tested against selected gram-positive, gram-negative bacteria, and Candida albicans yeast and compared with activity of previously reported [M(IP-2-ac)₂(H₂O)₂]·2H₂O (M = Co, Ni, Mn, Cd) complexes.

Graphical abstract

Keywords:

• Imidazo[1,2-a]pyridine
• Zinc(II) complexes
• X-ray structures
• Vibrational spectra
• Thermal stability
• Antibacterial activity

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by a statutory activity subsidy from the Polish Ministry of Science and Higher Education for the Department of Chemistry of Wroclaw University of Technology. We also gratefully acknowledge the instrumental grant 6221/IA/119/2012 from Polish Ministry of Science and Higher Education, which supported our Integrated Laboratory of Research and Engineering of Advanced Materials where IR measurements were performed and Wrocław Center of Networking and Supercomputing for the generous allotment of computer time.