Syntheses and characterizations of calcium and strontium based coordination compounds with the 5-(2-pyridyl)tetrazolate ligand, respectively exhibiting extended 1 D and 2 D structures

Coordination compounds of calcium and strontium with 5-(2-pyridyl)tetrazolate ligand (2-PTZ) were obtained by the reactions of the respective metal nitrates with 2-cyanopyridine, 2-cyanoacetamide and sodium azide in aqueous solutions. Both the complexes were found to have similar composition i.e. [M(2-PTZ)2(H2O)4]n.2nH2O where M = Ca(II) (1) and Sr(II) (2). The products were characterized by FT-IR spectra and single-crystal X-ray diffractions. Their photoluminescences, bandgaps, and thermal properties have been studied. Single crystal X-ray diffractions revealed that both 1 and 2 have distorted square anti-prismatic molecular geometries wherein the two 2-PTZ anions act as bidentate ligands by coordinating via their pyridine-N and tetrazole-N atoms. In both the molecules six water molecules, of which four acting as monodentate ligands, and the remaining two in the lattices were present. The lattice H2O molecules significantly stabilized the structures through N··H··O hydrogen bonds with the 2-PTZ ligands in the structures. Compound 2 (with around 50% decomposition) shows better thermal stability than calcium-based compound 1(72% decomposition). Graphical Abstract [Display omitted] .