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

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.