Zinc(ii) coordination compounds based on in situ generated 3-(5H-tetrazol)benzaldehyde with diverse modes: hydrothermal syntheses, crystal structures and photoluminescent properties

Abstract

Four Zn(II) tetrazolate coordination compounds have been hydrothermally synthesized and structurally determined by single-crystal X-ray diffraction. They are formulated as [Zn(3-tzbd)₂]_n·nH₂O (1), [Zn₂(3-tzbd)₂(OH)₂(4,4′-bipy)]_n·nH₂O (2), [Zn₂(3-tzbd)₃(N₃)(4,4′-bipy)₂]_n·nH₂O (3) and Zn₂(3-tzbd)₄(phen)₂ (4), where 3-Htzbd = 3-(5H-tetrazol)benzaldehyde. The 3-tzbd⁻ ligand, which was in situ generated through a [2 + 3] cycloaddition reaction of nitrile and azide, displays diverse coordination modes. Compound 1 exhibits a (4,4)-connected two-dimensional (2D) layer generated by the linkage of dinuclear units of [Zn₂(μ₂-3-tzbd)₂] and μ₂-3-tzbd⁻ ligands. In 2, Zn(II) atoms are connected by μ₂-3-tzbd⁻ ligands and μ₃-OH⁻ anions to form unusual double-stranded stair-like chains, which are further linked by 4,4′-bipy to create a 2D sheet. Compound 3 features an unprecedented one-dimensional (1D) four-legged, triple-ladder chain composed of tetranuclear units [Zn₄(μ₂-3-tzbd)₄(μ₂-N₃)₂]. Two Zn(II) atoms in 4 are bridged by μ₂-3-tzbd⁻ ligands to result in an isolated dinuclear structure. In addition, the luminescent properties of 1–4 were investigated in the solid state at room temperature. The relevant density of states (DOS) calculation results show that their photoluminescence mainly originates from ligand-centered emission and is dependent on the organic ligand incorporated into the compounds.