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

Abstract

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 DSNPDC^4– 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.