Flexible ligands and structural diversity:: Isomerism in Cd(NO3)2 coordination polymers

The ligands 1,4-bis(2-pyridylmethylsulfanylmethyl)benzene (L1) and 2,5-bis(2-pyridylmethylsulfanylmethyl)pyrazine (L2) were treated with Cd(NO3)(2)center dot 4H(2)O in metal-to-ligand ratios of 1:1 and 2:1, respectively; L2 was also treated with CdCl2 center dot 2.5H(2)O in a 2:1 ratio. All products were found to be coordination polymers. The crystal structures of {[Cd(L1)(NO3)(2)]center dot CH2Cl2}(infinity) (1a), {[Cd(L1)(NO3)(2)]center dot 4/3CH(3)CN}(infinity) (1b), {[Cd-2(L2)(NO3)(4)]center dot 2CH(3)CN}(infinity) (2 center dot 2CH(3)CN), and {[Cd-2(L2)Cl-4]center dot 2CH(2)Cl(2)}(infinity) (3 center dot 2CH(2)Cl(2)) were determined. Compounds la and 1b were found to be conformational supramolecular isomers. The structure of 1b displayed topological isomerism with two isomeric polymer chains, 1b(1) and 1b(2), in the one crystal forming a single supramolecular array. The structure of 2 center dot 2CH(3)CN showed Cd2(L2) units linked together by nitrates bridging between the Cd(II) centers in a mode previously not seen in Cd(II) compounds. The overall structure of 3 center dot 2CH(2)Cl(2) was found to be similar to that of 2-2CH(3)CN despite the presence of different anions and solvent molecules. Powder X-ray diffraction was used to investigate the nature of bulk preparations of compounds 1-3.