Lanthanide coordination polymers constructed from infinite rod-shaped secondary building units and flexible ligands

Three lanthanide coordination polymers constructed from infinite rod-shaped secondary building units (SBUs), [Nd-2(H2O)(2)(cis-chdc)(2)(trans-chdc)]center dot 2H(2)O (1), Nd-2(H2O)(4)(trans-chdc)(3) (2), and [Sm-2(H2O)(2)(cis-chdc)(trans-chdc)(2)]center dot 4H(2)O (3) (chdcH(2)= 1,4-cyclohexanedicarboxylic acid), were hydrothermally synthesized and structurally characterized. The structures of 1-3 are modulated by different ratios of the cis and trans configurations of chdc(2-) ligands, which was achieved by temperature control in the hydrothermal reactions. Crystal-structure analysis revealed that 1 is a four-connected pcu-type rod packing network built from cross-linking of rod-shaped neodymium-oxygen SBUs by cis- and trans-chdc(2-) ligands in a 2:1 ratio, 2 displays a complicated six-connected hex-type rod packing structure built by connection of rod-shaped neodymium-oxygen SBUs and trans-chdc(2-) ligands, and 3 features an unprecedented five-connected rod packing pattern constructed from rod-shaped samarium-oxygen SBUs and cis- and trans-chdc(2-) ligands in a 1:2 ratio.