Two 1D double-chain silver coordination polymers constructed by Ag-Ag bonds: Synthesis, structure and properties

Two new one-dimensional (1D) double-chain Ag(I) coordination polymers, namely: {[Ag(Hcn)(bpy)]·2CH3OH}n (1), [Ag2(Hidc)(H2O)2]n (2) (Hcn = 2-hydroxycinnamate, bpy = 4,4′-bipyridine, Hidc = 4,5-imidazoledicarboxylate), were synthesized by volatilization method and characterized by single-crystal X-ray diffraction, elemental analysis, IR and UV–vis spectra. Single-crystal analyses show that although two Ag(I) CPs are both 1D double-chain structure constructed by Ag-Ag bonds, CP 1 is linear, while CP 2 is zigzagged. This difference in the structure may be due to the symmetry of the repeat unit of the Ag(I) CPs and the linkage pattern of the Ag-Ag bonds, in which the repeat unit of CP 1 is symmetric, whereas that of CP 2 is asymmetric. The fluorescence properties of the ligands and CPs 1-2 in the solid-state were studied. The fluorescence peaks of the two Ag(I) CPs were weakened compared to the ligands, which is attributed to ligand-centered fluorescence. The partial quenching of the aggregates may be due to the Ag-Ag interactions. In addition, cyclic voltammograms of CPs 1-2 indicated an irreversible Ag+/Ag couple with the order of reversibility being 1 > 2.