A (3,9)-connected cadmium 1,2,4-triazolate framework based on a trinuclear inorganic cluster

Abstract

Hydrothermal reaction of 1,2,4-triazole with CdCl₂ · 2.5H₂O generated a 3-D metal-organic framework, {[Cd₃Cl₂(Trz)₄] · H₂O} _n (1) (Trz = 1,2,4-triazole), which was characterized by elemental analysis, FT-IR, X-ray powder diffraction, X-ray single-crystal diffraction, TG/DTA, and photoluminescence measurements. Compound 1 crystallizes in the orthorhombic system, space group Pnma, a = 16.906(3) Å, b = 8.3151(17) Å, c = 13.080(3) Å, V = 1838.6(6) ų, Z = 4. Cd(1) is coordinated by four nitrogen atoms and one chloride to form a distorted trigonal-bipyramidal geometry. Cd(2) is an octahedron defined by four triazole nitrogen atoms and two chlorides. Two Cd(2) and one Cd(1) are linked by μ ₃-Cl(1) to give a [Cd₃Cl] cluster, which is connected by μ ₂-Cl(2) to generate a 1-D inorganic chain. The 1-D inorganic chains are extended by μ ₃-Trz to form a 2-D hybrid layer in the b, c-plane, which is ultimately linked by residual triazole ligands to give a 3-D framework. The [Cd₃Cl] clusters and the Trz ligands can be regarded as 9- and 3-connected nodes, which lead to an unusual (3,9)-connected net with Schläfli symbol of (4²³ · 6¹³)(4³). The solid 1 exhibits high thermal stability and shows strong blue fluorescence emission at 410 nm in the solid state at ambient temperature.

Keywords:

• Hydrothermal reaction
• 1,2,4-Triazole
• Crystal structure
• Fluorescence
• Topology

Acknowledgments

The work was financially supported by the National Natural Science Foundation of China (no. 20801033), the Natural Science Foundation of Shaanxi Province (no. 2010JQ2010), and the Youth Foundation of School of Chemistry and Materials Science, Shaanxi Normal University.