((1H-tetrazol-5-yl) methyl) pyridine-based metal coordination complexes: in situ tetrazole synthesis, crystal structures, luminescence properties

Abstract

Six novel transition metal coordination complexes, [Cu(3TMP)] (1), [Zn(3TMP)Cl] (2), [Cd₃(3TMP)₄(N₃)₂]·0.38H₂O (3), [Zn₃(4TMP)₂(OH)₂(H₂O)]·2(NO₃) (4) and [M₂(4TMP)(OH) (H₂O)(SO₄)] (M = Zn (5), M = Cd (6)) (3HTMP = 3-((1H-tetrazol-5-yl) methyl) pyridine; 4HTMP = 4-((1H-tetrazol-5-yl) methyl) pyridine), have been hydrothermally synthesized through in situ tetrazole synthesis. These complexes have been structurally characterized by single crystal and powder X-ray diffraction elemental analyses, Fourier transform infrared spectroscopy as well as thermal studies. Complexes 1–6 are two or three-dimensional (3D) frameworks with structural diversity owing to the versatile coordination modes of the in situ generated flexible ligands. Complex 1 presents a reticular structure consisting of two-dimensional (2D) layers formed by the linkage between the pyridine rings and [Cu–tetrazole–Cu] wave-like chains. Complex 2 features a 3D framework built up by two kinds of helical chains composed of Zn(II) and the flexible ligand 3TMP. Complex 3 exhibits a 3D framework built up from 3TMP ligands and trinuclear [Cd₃(N₃)₂] building units. Complex 4 crystallizes as a 3D coordination complex constructed from two-dimensional layers and the linkers of 4TMP ligands, with NO₃⁻ anions situated in the channels. Complexes 5 and 6 exhibit a 3D framework constructed from {M₂(4TMP)(OH)}_nⁿ⁻ (M = Zn (5), M = Cd (6)) layers and sulfate anions. In addition, the counterions, such as the Cl terminal ligand in 2, the N₃ terminal ligand in 3, the μ₂-OH bridging ligand in company with free NO₃⁻ anions in 4, and the μ₃-OH bridging ligand in company with free SO₄²⁻ anions in 5 and 6, have decisive influence on the dimensionality and functionality of the final complexes. Furthermore, the solid state luminescence properties of these complexes have been investigated.