Syntheses, structures, and photoluminescent properties of a series of zinc(ii)–3-amino-1,2,4-triazolate coordination polymers constructed by varying carboxylate anions

Abstract

To explore the influence of different carboxylate ligands on the structures of metal–organic frameworks (MOFs), five novel Zn(II) coordination polymer compounds, namely, {[Zn(atz)(bia)]}_n (1), {[Zn₃(atz)₃(tpa)_3/2]}_n (2), {[Zn₂(atz)₂(pda)]}_n (3), {[Zn₄(atz)₂(btc)]·4H₂O}_n (4) and {[Zn₂(atz)₂(btec)]·H₂O}_n (5) have been successfully obtained by introducing various secondary auxiliary ligands in Zn(II)–L systems, characterized by elemental analysis, FT-IR, thermogravimetric analysis (TGA), powder X-ray diffraction (PXRD) and single-crystal X-ray diffraction (Hatz = 3-amino-1,2,4-triazolate, Hbia = benzoic acid, H₂tpa = 1,4-terephthalic acid, H₂pda = 1,4-benzenediacetic acid, H₃btc = 1,3,5-benzenetricarboxylate, H₄btec = 1,2,4,5-benzenetetracarboxylic). Compound 1 features a 2D layer with (4.8²) topology, which is further stabilized by hydrogen bonds between the uncoordinated amino groups and uncoordinated oxygen atoms from bia ligands. Compound 2 exhibits a 3D 3,4-connected framework with {4.8².10³}{4.8²} topology, constructed from Zn(II) ions and μ₃-atz ligand. Compound 3 displays a 3D 3,4-connected network with {4.6.8}{4.6².8³} topology. Compound 4 possesses a 3D 9-nodal network with a point symbol of {4.8.9}₂{4.8²}{4.8³.9.10}{5.8.9}₄{5.8²}. Compound 5 shows a 3D 3,4,4-connected framework with {4.8²}₄{4².8³.10}₂{8⁴.10²} topology. The diverse structures of these five complexes demonstrate that the skeleton of carboxylate ligands have a significant impact on the construction of MOFs. Moreover, the luminescence properties of complexes 1–5 were investigated in the solid state.