Syntheses, structures, and optical properties of novel zinc(II) complexes with multicarboxylate and N-donor ligands

Five novel coordination polymers [Zn-2(OA)(4,4'-bipy)(H2O)] center dot 0.5(4,4'-bipy) (1), [Zn-2(OA)(dib)(H2O)] center dot H2O (2), [Zn-2(OA)(bbi)(2)] center dot 3H(2)O (3), [Zn-2(OA)( phen) 2(H2O)] (4) and [Zn-4(OA) 2(2,2'-bipy) 2(H2O)] center dot 2H(2)O (5) were obtained by hydrothermal reactions of Zn(NO3)(2) center dot 6H(2)O with a V-shaped multicarboxylate ligand 3,3', 4,4'-oxydiphthalic acid (H(4)OA) and a series of N-donor ligands, namely 4,4'-bipyridine (4,4'-bipy), 1,4- di(1-imidazolyl) benzene (dib), 1,1'-(1,4-butanediyl)bis(imidazole) (bbi), 1,10-phenanthroline (phen), 2,2'-bipyridine (2,2'-bipy). The structures of the complexes were established by single-crystal X-ray diffraction analysis. Complex 1 exhibits a robust 3D porous structure with uncoordinated 4,4'-bipy molecules filling the cavities. Complexes 2 and 5 show a complicated 3D framework, while complexes 3 and 4 have a 2D network and a 1D helical chain structure, respectively. The results indicate that the multicarboxylate OA(4-) ligand can adopt varied coordination modes in the formation of the complexes and the influence of the N-donor ligand on the structure of the complexes is discussed. The photoluminescence properties of H4OA and 1-5 were studied in the solid state at room temperature. Moreover, nonlinear optical measurements showed that 5 displayed a second-harmonic-generation (SHG) response of 0.5 times of that for urea. The results suggested that the configuration and flexibility of the ligands play a key role in directing the related properties of the complexes.