Two novel indium coordination polymers derived from 2,6-pyridinedicarboxylate ligand: Syntheses, structures and photoluminescent properties

Two indium coordination polymers (CPs) with different structures InCl(2,6-pdc)(H2O) (1) and In2Cl4(2,6-pdc)(4,4′-bipy)2 (2) were synthesized by the reactions of InCl3 with 2,6-pyridinedicarboxylic acid (2,6-H2pdc) and 4,4′-bipyridine (4,4′-bipy) ligands. Compound 1 features a two dimensional (2D) network with the rhombic windows constructed from novel [In2O6(H2O)2Cl2(2,6-pdc)2] dimeric building units and 2,6-pdc2− ligands. Compound 2 possesses a 2D layer structure which is accomplished by connecting the wavy chains to the distorted 4,4′-bipy ligands. The different structures of 1 and 2 show the predominant influence of chlorine atoms and organic ligands. In addition, non-classical hydrogen-bond (C–H⋯Cl) interactions also play an important role in the formation of supramolecular architectures, for instance, to link 2D entities to 3D frameworks. These new In(III) CPs show intense fluorescence emission with long lifetimes in the solid state at room temperature.