Two Zinc(II) Complexes with 1D Chain and 2D Layer Directed by Competitive Coordination of the Mixed Ligands: Syntheses, Crystal Structures, and Fluorescent Properties

Two new competitive coordination-directed zinc(II) complexes, [Zn-2(bpp)(2)(na)(4)](n) (1) and [Zn(bpp)(2)(nas)(2)](n) (2) (bpp = 1,3-bi(4-pyridyl)propane, na(-) = 1-naphthoate, and nas(-) = 2-aminonaphthalene-1-sulfonate), were hydrothermally synthesized by varying carboxylate- or sulfonate-containing coligands. Structural analyses reveal that complex 1 modified by terminal na(-) spacers possesses a bent one-dimensional chain bridged by ditopic bpp linkers. By contrast, complex 2 with two monodentate nas(-) ligands exhibits a two-dimensional layered structure extended by four equatorial bpp connectors. Obviously, the increase on the dimensionality of 2 than 1 is significantly resulting from the competitive coordination of the two mixed ligands with differently tunable binding groups to variable metal polyhedra. In addition, both complexes with analogously high thermal stability display strong fluorescent emissions at room temperature resulting from the ligand-to-metal or intraligand charge-transfer, suggesting their hopeful applications as efficient fluorescent materials.