Synthesis and structural characterization of two new copper(II) complexes with thiazoline derivative ligands: Influence of the coordination on the phagocytic activity of human neutrophils

Two new copper(II) complexes dichloro[2-(3,4-dichlorophenyl)imine-κN-(2-thiazolin-κN-2-yl)thiazolidine]copper(II) [CuCl2(TdTn)] (1) and dichloro[2-(3,4-dichlorophenyl)imine-κN-(2-thiazolin-κN-2-yl)tetrahydrothiazine]copper(II) [CuCl2(TzTn)] (2) were synthesized, then characterized by elemental analysis, UV–Vis–NIR diffuse reflectance, electron paramagnetic resonance (EPR) spectroscopy, magnetic susceptibility, infrared spectroscopy, and finally their crystal structures determined by X-ray diffractometry. The structural determination of [CuCl2(TzTn)] (2) was made by conventional single-crystal diffractometry, whereas the procedure followed to resolve the crystal structure of [CuCl2(TdTn)] (1) by means powder diffractometry using direct-space methods with a ‘Monte–Carlo/parallel tempering’ search algorithm. A final refinement of the crystal structure was performed using the Rietveld method. It was found that the environment around the copper(II) ion for both complexes can be described as having a distorted tetrahedral geometry, with the metallic atom coordinated with two chlorides, one imine nitrogen and one thiazoline nitrogen. The biological activity of the complexes, inorganic salt and their ligands has been evaluated by examining their phagocytic activity on human neutrophils. This activity enhances in the case of the samples treated with [CuCl2(TdTn)] (1) and [CuCl2(TzTn)] (2) with respect to the ones to which CuCl2, TdTn or TzTn was added.