The crystal structures of bis[1-ethyl-6-fluoro-4-oxo-7-(piperazin-1-ium-4-yl)-1,4-dihydroquinoline-3-carboxylato]copper(II) sulfate heptahydrate, [Cu(C 16 H 18 FN 3 O 3 ) 2 ]SO 4 ·7H 2 O or [Cu(nor) 2 ]SO 4 ·7H 2 O (nor is norfloxacin), and bis{1-[2-(ethylsulfonyl)ethyl]-2-methyl-5-nitroimide}dinitratocopper(II), [Cu(NO 3 ) 2 (C 8 H 13 N 3 O 4 S) 2 ] or [Cu(NO 3 ) 2 (tnz) 2 ] (tnz is tinidazole), were solved by X-ray diffraction. Both complexes crystallize in the space group P 2 1 / c , with Z = 4 (for nor) and Z = 2 (for ntz) molecules per unit cell. In [Cu(nor) 2 ]SO 4 ·7H 2 O, the Cu II ion is at the centre of a square-planar environment, trans coordinated to two independent norfloxacin molecules in the zwitterionic form acting as bidentate ligands through one of the carboxyl (cbx) and the carbonyl (cb) O atoms. The solid is further stabilized by an extensive network of N—H...O(sulfate), N—H...O(cbx), N—H...O W , O W —H...O(sulfate) and O W —H...O W hydrogen bonds. The [Cu(NO 3 ) 2 (tnz) 2 ] complex is centrosymmetric, with the Cu II ion in a square planar environment, coordinated to a tinidazole molecule acting as a monodentate ligand through its imidazole N atom and to one nitrate O atom. The vibrational FT–IR absorption spectra and thermal behaviour of the complexes were also studied and are briefly discussed based on the crystal structures.