The 2-D double layer structures of indium–benzenemulticarboxylate coordination polymers with green fluorescence

Abstract

Two coordination polymers, [In(btc)(2,2′-bpy)(H 2O)] n · nH 2O ( 1) and [In 2(btec)(2,2′-bpy) 2Cl 2] n ( 2) (H 3btc = 1,3,5-benzenetricarboxylic acid, H 4btec = 1,2,4,5-benzenetetracarboxylic acid, 2,2′-bpy = 2,2′-bipyridine), have been prepared under hydrothermal conditions. Single-crystal X-ray diffraction analyses reveal that compounds 1 and 2 consist of two-dimensional double layer structures with (3, 3) grids and (4, 2) grids, respectively. The grids along two different directions in 1 are of the opposite chirality, while the interactions of double-layer sheets in 2 create a three-dimensional supramolecular network with one-dimensional tunnels. The additional green luminescences for both 1 and 2 in the solid state at low temperature imply the red shift of emission energy in the compounds, which may derive from LMCT. Their X-ray powder diffractions and thermogravimetric analyses are also discussed.