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

Abstract 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 [ZnCl 2 (H 2 O)(PzTz)] ( 1 ), [ZnCl 2 (DMPzTz)] ( 2 ) and [ZnCl 2 (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 ZnCl 2 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.