Hydrostable coordination polymers of a methyl-functionalized 4,4'-bipyridine ligand: structure, stability, magnetic and luminescent properties

The reactions of aromatic dicarboxylic acids and methyl-functionalized 4,4'-bipyridine ligands with metal salts under hydrothermal conditions generated four structurally diverse cobalt(II), zinc(II) and cadmium(II) coordination polymers, [Co(CH3-BDC)(dmbpy)(0.5)] (n) (1), [Cd(OH-HBDC)(2)(dmbpy)] (n) (2), [Zn(NDC)(dmbpy)] (n) , (3) and {[Cd(DBA)(dmbpy)(0.5)]center dot 2H(2)O} (n) (4) (CH3-H2BDC = 5-methylisophthalic acid, OH-H2BDC = 5-hydroxyisophthalic acid, H2NDC = 1,4-naphthalenedicarboxylic acid, H(2)DBA = 4,4'-methylenedibenzoic acid, dmbpy = 2,2'-dimethyl-4,4'-bipyridine). All four complexes have been structurally characterized by X-ray crystallography. Complex 1 shows a 3D jsm topology structure with two 1D channels parallel to the a and b axes. Complex 2 has a zigzag chain in which the OH-HBDC ligands point alternately up and down. Complexes 3 and 4 show 2D (4,4) networks when the dinuclear metal centers and their ligands are regarded as nodes and linkers, respectively. Complex 3 also shows twofold interpenetration with 1D channels along the b axis. Two nets of complex 4 interlock in parallel, giving rise to a polycatenated layer (2D -> 2D). Thermogravimetric and chemical stabilities, magnetic and luminescent properties of these complexes were investigated.