1,2-Cyclohexanedionedioxime as a useful co-ligand for fabrication of one-dimensional Zn(II) and Cd(II) coordination polymers with wheel-and-axle topology and luminescent properties

The combination of 1,2-cyclohexanedionedioxime (NioxH(2)) and carboxylate-containing ligands resulted in Zn(II) or Cd(II) robust metal building blocks which being coupled with the flexible pyridine ligands fabricated five one-dimensional (1D) coordination polymers {[Cd(CHOO)(2)(NioxH(2))(bpe)]center dot DMF}(infinity) (1), [Cd(CHOO)(2)(NioxH(2))(dps)](infinity) (2), [Zn(CH3COO)(2)(NioxH(2))(dps)](infinity) (3), [Cd(CH3COO)(2)(NioxH(2))(dps)](infinity) (4), and {[Zn(pyta)(2)(NioxH(2))]center dot DMF}(infinity) (5) (where bpe 4,4'-bipyridine ethane, dps 4,4'-dipyridylsulfide, Hpyta (4-pyridylthio) acetic acid, DMF N, N-dimethylformamide), whose crystal structures were determined by single crystal X-ray diffraction. The stability of compounds 1 and 5 to loss of DMF as a guest has been addressed experimentally, and the crystal-to-crystal transformation observed for 1 resulted in the guest free 1D polymer [Cd(CHOO)(2)(NioxH(2))(bpe)](infinity) (1a) which maintains its coordination network with the 10.3% unit cell volume contraction, while compound 5 remains unchangeable under the same conditions. Compounds 1, 5 and the dioxime-free 1D polymer [Cd(pyta)(2)(H2O)](infinity) (6) display blue luminescence upon excitation with ultraviolet light. The emission intensity of the guest-loaded complex 1 is effectively reduced in comparison with the previously reported DMF free analogues [Zn(CH3COO)(2)(NioxH(2))(bpe)(H2O)](infinity) and [Cd(CH3COO)(2)(bpe)(H2O)](infinity).