Zinc(II) complexes with novel 1,3-thiazine/pyrazole derivative ligands: Synthesis, structural characterization and effect of coordination on the phagocytic activity of human neutrophils

The new ligands 2-(1-pyrazolil)-1,3-thiazine (PzTz), 2-(3,5-dimethyl-1-pyrazolil)-1,3-thiazine (DMPzTz) and 2-(3,5-diphenyl-1-pyrazolil)-1,3-thiazine (DPhPzTz) and the complexes ZnCl₂(H₂O)(PzTz)] (1), ZnCl₂(DMPzTz)] (2) and ZnCl₂(DPhPzTz)] (3) have been isolated and then characterized by elemental analysis, IR spectra and UV-Vis spectroscopy. Besides, the crystal structure of ligands PzTz and DPhPzTz and complexes 1-3 have been determined by single-crystal X-ray diffraction. In 1, the geometry around the Zn(II) atom can be considered a highly distorted trigonal bipyramid, with the metallic atom bonded to two chlorine atoms, one water molecule and one bidentate PzTz ligand. In 2 and 3, the environment around the metal ion can be described as a distorted tetrahedron with the zinc atom coordinated to one bidentate organic ligand molecule and two chloro ligands. In addition, the phagocytic function of human neutrophils treated with complexes 1-3, their organic ligands and ZnCl₂ has been evaluated. The activity of cells enhanced in samples treated with 1, 2 and 3 with respect to the ones to which the inorganic salt, PzTz, DMPzTz or DPhPzTz were added.