Synthesis, structure, and photoluminescence of a (4,6)-connected Cu(I)–CN–triazolate framework built with a unique heptanuclear hybrid cluster

Abstract

A 3-D Cu(I)–CN–triazolate hybrid coordination polymer, {Cu9(NH2-BPT)2(BPT)2(CN)7}n (1) (NH2-BPT = 4-amino-3,5-bis(3-pyridyl)-1,2,4-triazole, BPT = 3,5-bis(3-pyridyl)-1,2,4-triazole), has been synthesized via self-assembly of NH2-BPT, CuCN, and K3Fe(CN)6 under hydrothermal conditions. Single-crystal X-ray diffraction data show that four of the five independent copper centers in 1 have a three-coordinated trigonal coordination geometry, and the remaining copper center has a two-coordinated linear geometry. Three Cu ions are linked by one cisoid-BPT and two CN− to form a 16-membered ring subunit, which is joined by the two-coordinate copper center via the triazole N(4)-position to generate an unprecedented [Cu7(BPT)2(CN)4] hybrid heptanuclear cluster. Each heptanuclear motif is linked to two adjacent [Cu7] clusters through four CN− anions, and further to four [Cu–CN–Cu] binuclear clusters through two transoid-NH2-BPT ligands. Each of these [Cu–CN–Cu] units is linked to four neighboring heptanuclear motifs. The overall geometry is a 3-D (4,6)-connected topological framework with Schläfli symbol of (44 × 62)(44 × 610 × 8). Compound 1 also exhibits high thermal stability and strong green fluorescence emission at 536 nm in the solid state.