N-donor ligand mediated assembly of divalent zinc and cadmium coordination polymers based on 2,3,2′,3′-thiaphthalic acid: structures and properties

A series of five metal-organic frameworks, namely, {[Cd-2(tdpa)(H2O)(3)]center dot H2O}(n) (1), {[Cd-2(tdpa)(bpe)(H2O)(3)]}(n) (2), {[Cd-2(tdpa)(bix)]}(n) (3), {[Cd-2(tdpa)(bpg)(H2O)(4)]center dot 3H(2)O}(n) (4) and {[Zn-4(tdpa)(2)(bpy)(2)(H2O)(11)]center dot 4H(2)O}(n) (5) have been hydro(solvo)thermally synthesized through the reaction of 2,3,2',3'-thiaphthalic acid (H(4)tdpa) with divalent zinc and cadmium salts in the presence of ancillary nitrogen ligands (bpy = 4,4'-bipyridine, bpg = meso-alpha,beta-bi(4-pyridyl) glycol, bpe = 1,2-di(pyridin-4-yl)ethane and bix = 1,4-bis((1H-imidazol-1-yl)methyl)benzene) and structurally characterized by elemental analysis, IR and X-ray diffraction. In complexes 1, 2 and 3, rod-shaped {Cd12Cd22C6O10}(n) Cd-chain secondary building units (SBUs) have been formed. For 1, such rod-shaped SBUs are linked together through tdpa(4-) itself to form a metal-organic layer. For 2 and 3, such metal-organic SBUs are further associated together by bpe or bix ligands in four orientations to form a robust 3D metal-organic network, respectively. In compound 4, a 3D Cd-tdpa metal-organic network is accomplished through tdpa(4-) anion ligands, and further stabilized by bpg. In complex 5, zinc atoms are bridged by tdpa(4-) anion ligands and bpy to form infinite Zn-tdpa chains. Luminescence and thermal analysis of these complexes have also been investigated.