Synthesis, characterization and photophysical properties of some water soluble Zn(II) azide complexes with (E)-2,4-dimethoxy-N-((pyridin-2-yl)methylene)benzenamine derived from 2-pyridinecarboxaldehyde

Five new zinc(II) azide complexes with the composition [Zn(N₃)₂(Lⁿ)], where Lⁿ = (E)-2,4-dimethoxy-N-((pyridin-2-yl)methylene)benzenamine, are reported herein. The complexes were characterized using UV-vis, fluorescence, IR, and ¹H NMR spectroscopy, along with elemental analysis. The single-crystal structural analysis of compound 1 is presented. The mononuclear Zn(II) complex crystallized in the monoclinic system with the centrosymmetric space group P₂1/n. The asymmetric unit of complex 1 consists of two crystallographically independent molecules with quite similar geometries. The five-coordination geometry of the Zn(II) ions in 1 is irregular, best described as halfway between trigonal bipyramidal and square pyramidal geometries. Efforts to obtain single crystals of compounds 2–5 suitable for X-ray crystal structure analysis were unsuccessful. However, based on spectroscopic data and the structures of related zinc(II) complexes reported in the literature, complex 2 is proposed to have a geometry similar to that of complex 1, and complexes 3–5 are anticipated to have a four-coordinated tetrahedral geometry. All complexes were obtained in moderate-to-good yields and behave as non-electrolytes in acetonitrile solution. UV-vis and fluorescence spectral studies of complexes 1–5 indicate ligand-to-ligand (intra-ligand, π-π*) charge transfer transitions.