Hybrid open frameworks (MIL-n).: Part 4 -: Synthesis and crystal structure of MIL-8, a series of lanthanide glutarates with an open framework, [Ln(H2O)]2[O2C(CH2)3CO2]3•4H2O

The first series of rare-earth carboxylates with an open framework has been prepared hydrothermally (180 degrees 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 [Nd-III(H2O)](2) [O2C(CH2)(3)CO2](3). 4H(2)O 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) Angstrom, b = 15.1841(3) Angstrom, c = 19.8803(3) Angstrom, beta = 93.762(1)degrees (final agreement factors R-1 = 0.0279, wR(2) = 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.