Three cadmium-5,7-disulfonate-1,4-naphthalenedicarboxylate coordination polymers: syntheses, structures and photoluminescence

Three cadmium(II) coordination polymers constructed from 5,7-disulfonate-1,4-naphthalenedicarboxylate and N-containing ligands, {[Cd2(DSNPDC)(phen)(H2O)4]·2.5H2O}n (1), {[Cd2(DSNPDC)(phen)2(H2O)4]·3H2O}n (2) and [Cd2(DSNPDC)(bpy)2(H2O)4]n (3) (H4-DSNPDC = 5,7-disulfonate-1,4-naphthalenedicarboxylic acid, phen = 1,10-phenanthroline, and bpy = 2,2′-bipyridine), were synthesized and characterized. Compound 1 displays a two-dimensional (2D) layered structure. In 2 and 3, the dinuclear [Cd2(COO)2] units are connected by DSNPDC4– ligands to generate one-dimensional (1D) chains. Due to the presence of the terminal chelating phen/bpy ligands, all compounds show low dimensional structures. Compounds 1–3 exhibit fluorescence emissions centered at 378, 419 and 376 nm, respectively, which are assigned to ligand-centered emissions or ligand-to-metal charge transfer.