Fluorite Topology in Lanthanoid Coordination Polymers with Di- and Trimetallic Building Blocks

Reaction of the pseudotetrahedral tetracarboxylic acid proligand tetrakis(4-carboxyphenyl)silane (H4L) with salts of various lanthanoid metals has afforded three new lanthanoid coordination polymers: {[H3O](2)[Ce-2(L)(2)(H2O)(2)]center dot 2DMF center dot 2H(2)O}(infinity) (1), {[Eu3L2(NO3)(DMF)(4)(H2O)]center dot 0.5DMF center dot 6H(2)O}(infinity) (2), and {Eu(HL)(DMF)(2)(H2O)]center dot DMF center dot 2.5H(2)O}(infinity) (3) (DMF = N,N'-dimethylformamide), which have been structurally characterized by single-crystal X-ray diffraction. Compounds 1 and 2 are both noninterpenetrated three-dimensional networks that display the rare fluorite (CaF2) topology. In compound 1, the fully deprotonated L4- ligands act as pseudotetrahedral 4-connecting nodes and dinuclear cerium-carboxylate building blocks act as 8-connecting nodes, while in compound 2 the L4- ligands and trinuclear europium-carboxylate units are 4- and 8-connecting, respectively. In contrast, compound 3 exhibits a two-dimensional layered structure with triply deprotonated HL3- ligands acting as 3-connecting units, linking single europium centers within each layer. Gas sorption studies of 2 show a high affinity of the pretreated microcrystalline solid for carbon dioxide gas.