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[Ce2(L)2(H2O)2]·2DMF·2H2O}∞ (1), {[Eu3L2(NO3)­(DMF)4(H2O)]·0.5DMF·6H2O}∞ (2), and {Eu­(HL)­(DMF)2(H2O)]·DMF·2.5H2O}∞ (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.