Cadmium-1,4-cyclohexanedicarboxylato coordination polymers bearing different di-alkyl-2,2'-bipyridines: syntheses, crystal structures and photoluminescence studies.

Four coordination polymers have been synthesized using self-assembly solution reactions under ambient conditions, reacting Cd(ii) ions with 1,4-cyclohexanedicarboxylic acid in the presence of different 2,2'-bipyridine co-ligands: {[Cd(H2O)(e,a-cis-1,4-chdc)(2,2'-bpy)]·H2O}n (1); [Cd2(H2O)2(e,a-cis-1,4-chdc)2(4,4'-dmb)2]n (2); {[Cd(e,a-cis-1,4-chdc)(5,5'-dmb)]·H2O·CH3OH}n (3) and {[Cd(e,e-trans-1,4-chdc)(4,4'-dtbb)]·CH3OH}n (4), where 1,4-chdc = 1,4-cyclohexanedicarboxylato, 2,2'-bpy = 2,2'-bipyridine, 4,4'-dmb = 4,4'-dimethyl-2,2'-bipyridine, 5,5'-dmb = 5,5'-dimethyl-2,2'-bipyridine and 4,4'-dtbb = 4,4'-di-tert-butyl-2,2'-bipyridine. Crystallographic studies show that compound 1 has a 1D structure propagating along the crystallographic b-axis; the Cd ion in 1 is six-coordinated with a distorted-octahedral coordination sphere. Compound 2 has two crystallographic different Cd ions and both are six-coordinated with a distorted-octahedral coordination sphere. Compound 3 exhibits a seven-coordinated Cd ion having a distinctive distorted-monocapped trigonal prismatic geometry. In compound 4, the Cd ion is also seven-coordinated in a distorted monocapped octahedral geometry. Compounds 2, 3 and 4 possess rhombic-shaped dinuclear units (Cd2O2) as nodes to generate larger cycles made up of four dinuclear units, a Cd4 motif, bridged by four 1,4-chdc ligands, accomplishing, thus, 2D structures. Remarkably, in compound 4 the 1,4-chdc ligand conformation changes to the equatorial, equatorial trans, unlike the other compounds where the bridging ligand conformation is the more typical equatorial, axial cis. The solid state luminescence properties of 1-4 were investigated; polymers 3 and 4 exhibited a strong blue emission (λem = 410-414 nm) compared to 1 and 2; structure-related photoluminescence is attributed to the degree of hydration of the compounds. Furthermore, Cd-polymer 3 suspended in acetone allows the fluorescence selective sensing of acetonitrile over common organic solvents such as alcohols and DMF, based on turn-on fluorescence intensity with a limit of 53 µmol L-1.

Synthesis and characterization of novel dinuclear copper(I) complexes. Dimerization of [CuL(PPh3)2] (L = methyl 3-hydroxy-3-(p-R-phenyl)-2-propenedithioate).

We report the synthesis of new copper(I) complexes 6a-e from methyl 3-hydroxy-3-(p-R-phenyl)-2-propenedithioate ligands. These complexes were characterized by IR and 1H, 13C, and 31P NMR spectroscopy. The expected O,S-coordination mode was confirmed by the X-ray diffraction studies of 6b and 6e. The unexpected dimerization of 6b-e leads to the formation of four novel dinuclear copper(I) compounds (7b-e). The dinuclear complex structure was fully established by the X-ray diffraction analysis of 7a, in which the presence of a Cu-Cu interaction was observed.