Syntheses, crystal structures and fluorescent properties of two 4,4'-dipyridylsulfide based zinc(II) and cadmium(II) helical complexes

Two allomeric helical coordination polymers, {[Zn(4,4'-dps)2(HSSA)(H2O)2] center dot 3(H2O)}n (1) and {[Cd(4,4'-dps)2(HSSA)(H2O)2] center dot 3(H2O)}n (2) (4,4'-dps = 4,4'-dipyridylsulfide, H3SSA = 5-sulfosalicylic acid), have been synthesized by similar experimental methods and characterized by elemental analysis, single-crystal X-ray diffraction, and fluorescence spectra. Both crystallize in monoclinic system, space group P21/n, with a = 11.7947(13) angstrom, b = 13.7475(15) angstrom, c = 20.183(2) angstrom, and Z = 4 for 1 and a = 11.940(7) angstrom, b = 14.068(8) angstrom, c = 20.323(12) angstrom, and Z = 4 for 2. In both complexes, the metal (ZnII for 1 and CdII for 2) are six-coordinate with a N3O3 donor set in a distorted octahedron. Half of the 4,4'-dps are 2-bridging, linking adjacent metal centers and forming P21/n dimensional helical structures along the b-axis. Fluorescence measurements show that 1 and 2 have medium fluorescent emission at 402 and 405 nm, respectively.