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Reaction of the pseudotetrahedral tetracarboxylic acidproligandtetrakis(4-carboxyphenyl)silane (H4L) with salts of variouslanthanoid 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 structurallycharacterized by single-crystal X-ray diffraction. Compounds 1and 2are both noninterpenetrated three-dimensionalnetworks that display the rare fluorite (CaF2) topology.In compound 1, the fully deprotonated L4–ligands act as pseudotetrahedral 4-connecting nodes and dinuclearcerium-carboxylate building blocks act as 8-connecting nodes, whilein compound 2the L4–ligands and trinucleareuropium-carboxylate units are 4- and 8-connecting, respectively.In contrast, compound 3exhibits a two-dimensional layeredstructure with triply deprotonated HL3–ligandsacting as 3-connecting units, linking single europium centers withineach layer. Gas sorption studies of 2show a high affinityof the pretreated microcrystalline solid for carbon dioxide gas. [ABSTRACT FROM AUTHOR]

A remarkably flexible, multifunctional, 2D coordination polymer exhibiting an unprecedented mode of reversible mechanical motion, enabling pores to open and close, is reported. Such multifunctional materials are highly sought after, owing to the potential to exploit coexisting electronic and mechanical functionalities that underpin useful technological applications such as actuators and ultrasensitive detectors. The coordination polymer, of composition Mn(F 4 TCNQ)(py) 2 (F 4 TCNQ = 2,3,5,6-tetrafluoro-7,7,8,8-tetracycanoquinodimethane; py = pyridine), consists of Mn(II) centers bridged by F 4 TCNQ dianions and coordinated by py molecules that extend above and below the 2D network. Exposure of Mn(F 4 TCNQ)(py) 2 , in its collapsed state, to carbon dioxide results in a pore-opening process at a threshold pressure for a given temperature. In addition to carbon dioxide, a variety of volatile guests may be incorporated into the pores, which are lined with electron-rich F 4 TCNQ dianions. The inclusion of electron-deficient guests such as 1,4-benzoquinone, nitrobenzene, maleic anhydride, and iodine into the pores is accompanied by a striking color change associated with a new host-guest charge-transfer interaction and an improvement in the semiconductor behavior, with the iodine adduct showing an increase in conductivity of almost 5 orders of magnitude. Experimental and density functional theory calculations on this remarkable multifunctional material demonstrate a reduction in the optical band gap with increasing electron affinity of the guest.