Anion-Dependent Crystallization of Four Supramolecular Cadmium Complexes: Structures and Property Studies

Solvothermal reactions of 4,4′-methylene-bis(3-hydroxy-2-naphthalene carboxylic acid) (H4mbna), heterocyclic bidentate ligands, and Cd(II) salts yielded four zero- to two-dimensional coordination complexes, [Cd(phen)2(H2O)2](H2mbna)·(H2O) (1), {[Cd4(H2mbna)8/2(phen)4]·2DMF}n (2), [Cd(H2mbna)(bipy)(H2O)]n (3), and (Δ,Δ)- [Cd(H2mbna)(bipy)2]n (4). Crystal structural analyses revealed that the zero-dimensional units of 1 are connected by hydrogen-bond interactions forming a two-dimensional double-layer with hollow structure. The dinuclear units in 2 are bridged by the carboxylate groups of H2mbna producing a two-dimensional nanoporous layer with the size about 11 × 15 Å2. The zigzag chains in 3 are linked by hydrogen bonds constructing the nanotube structure with the size about 11 × 13 Å2. The chiral chain in 4 is formed by the introduce of the Δ-configuration 2,2′-bipyridine ligands. The differences in the structures of the four complexes indicate that the anion of the metal salts might act as a template in the formation of the solid product. The thermal property studies show that all of the four complexes are thermally stable. The title complexes also displayed structure-related photoluminescence properties in the solid state.