Low-dimensional compounds containing bioactive ligands. Part XXI: Crystal structures, cytotoxic, antimicrobial activities and BSA binding of zinc complexes with 5-chloro-7-nitro-8-hydroxyquinoline

Abstract

Four new zinc(II) complexes containing molecules of 5-chloro-7-nitro-8-hydroxyquinoline (HClNQ), NH2(CH3)2[Zn(ClNQ)3]·DMF (1), K[Zn(ClNQ)3]·2DMF (2), {Na[Zn(ClNQ)(SO4)(H2O)]}n (3) and [Zn(ClNQ)2(H2O)2] (4), were prepared and characterized by IR and NMR spectroscopy, elemental analysis and single crystal X-ray analysis. Ionic complexes 1 and 2 have similar structures, in which Zn(II) atoms are coordinated by three chelate molecules of ClNQ via oxygen and nitrogen donor atoms forming rare fac isomers. The negative charge of the complex anions is balanced by uncoordinated NH2(CH3)2+ (1) and K+ cations (2). Complex 3 has a polymeric structure in which Zn(II) atom is penta-coordinated by one chelate molecule of ClNQ, one molecule of water and a pair of crystallographically equivalent sulfato ligands, which interconnect adjacent zinc atoms to form a zig-zag chain. The negative charge of the chain is balanced by sodium cations. In a molecular complex 4, equatorial plane is occupied by two chelate ClNQ molecules with nitrogen and oxygen atoms of the two ligands in an infrequent cis-arrangement and axial positions of a distorted octahedron occupy two aqua ligands. HClNQ and complexes 1, 3 and 4 were tested for their antiproliferative activity against HeLa, A549, MCF-7, MDA-MB-231, HCT-116 and Caco-2 cancer cell lines and their selectivity was verified using Cos-7 non-cancerous cell line. The results showed that the complexes exhibited poor nonselective antiproliferative activity. Antibacterial activity of HClNQ and complexes 1, 3 and 4 were tested, too. RIZD (relative inhibition zone diameter) and MIC (minimal inhibitory concentration) showed that complexes 1, 4 and HClNQ inhibited gram-positive bacteria S. aureus. Against gram-negative bacteria E. coli, only HClNQ and 1 were effective in tested concentration. Finally, BSA binding activity of complexes 1 – 4 was investigated by fluorescence quenching measurements.