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.

Three new pyrazole/1,3-thiazine derivative ligands and their zinc(II) complexes have been synthesized and structurally characterized. In addition, the influence of the complexes, ligands and inorganic salt in the phagocytic activity of human neutrophils have been studied.Figure optionsDownload as PowerPoint slideHighlights
► X-ray diffraction study shows that ligands behave as bidentate towards Zn(II).
► Influence of ligands, complexes and ZnCl2 on phagocytosis have been studied.
► Coordination to Zn(II) improve phagocytic activity of human neutrophils.
► No significant effect of substituents in biological activity has been observed.