Copper(II) Complexes with 5-Nitro-2-furoic Acid: Synthesis, Structure, Thermal Properties, and Biological Activity

Reaction of copper(II) acetate with 5-nitro-2-furoic acid (NO 2 -Hfur) and N-donor ligands 2,2'‑bipyridine (bpy) and pyridine (py) has resulted in complexes [Cu(NO 2 -fur) 2 (H 2 O) 2 ]·2H 2 O ( I ), [Cu(NO 2 -fur) 2 (py) 2 (H 2 O)] ( II ), and binuclear [Cu 2 (NO 2 -fur) 4 (bpy) 2 ]·H 2 O ( III ) whose structure was determined by X‑ray diffraction study. Cation Cu 2+ is in square-planar ( I ) or square-pyramidal ( II , III ) environment and has CN(Cu) = 4 ( I ) or 5 ( II , III ), respectively. Stability of complexes I – III in solid phase has been determined by synchronous thermal analysis, stability in solutions has been studied by electronic absorption spectroscopy. Compounds I and II are thermally stable (>100°С). The presence of nitro group in the complexes causes strong exothermal effects, whose intensity is leveled by donor ligand. The storage of solutions of the compounds in 5% glucose solution and 0.9% NaCl for 2 days according to UV spectroscopy causes no their degradation. Biological activity of complexes I – III was studied in vitro toward non-pathogenic strain M. smegmatis (behaves as a model for M. tuberculosis ); antimicrobial activity of compound II toward a number of Gram-positive and Gram-negative bacteria has been investigated.