F. Serpaggi and G. Férey
The first series of rare-earth carboxylates with an open framework has been prepared hydrothermally (180°C, 3 days) by the action of glutaric acid on the metal chlorides in the presence of base. The crystal structure of the neodymium compound [NdIII(H2O)]2[O2C(CH2)3CO2]3·4H2O has been determined by single-crystal X-ray diffraction. The composite material crystallizes in the monoclinic space group C2/c (no. 15) with a=8.1174(1) Å, b=15.1841(3) Å, c=19.8803(3) Å, β=93.762(1)° (final agreement factors R1=0.0279, wR2=0.0693). The organic-inorganic network is three-dimensional and consists of chains of edge-sharing rare-earth polyedra NdO8(H2O) along the [100] direction, linked together by the carbon chains along two directions. The connection involves the formation of channels parallel to the rare-earth chains in which weakly bonded water molecules are incorporated. The analogous compounds were obtained with Pr, Sm, Eu, Gd, Dy, Ho and Y.