Structure and mesomorphism of neodymium(III) alkanoates

The structural and thermal behavior of all members of the homologous series of neodymium(III) alkanoates, ranging from neodymium(III) butyrate to neod ymium(III) eicosanoate are described. Neodymium(III) butyrate monohydrate, Nd(C3H7COO)(3).H2O crystallizes in space group P (1) over bar (No. 2), Z = 2. The lattice parameters are a 9.824(7) Angstrom, b = 11.974(2) Angstrom, c = 14.633(2) Angstrom, alpha = 86.21(2)degrees, beta = 75.92(2)degrees, ga mma = 77.97(2)degrees. The crystal structure consists of ionic layers of ne odymium ions, separated by bilayers of butyrate anions. In the ionic layers , the neodymium ions are connected by bridging tridentate carboxylate group s to zigzag chains, whereas the chains are connected among themselves by br idging bidentate carboxylate groups. The two crystallographically different neodymium ions an both having coordination number 9, with a geometry close to a monocapped square antiprism. The structure of the higher homologues c an be derived from the structure of neodymium butyrate by extending the alk yl chains. These compounds have a lamellar bilayer structure with planes of neodymium(III) ions coordinated to the carboxylate groups and with the alk yl chains in an all-turns conformation. All homologous compounds from neody mium(III) pentanoate to neodymium(III) pentsdecanoate display a thermotropi c mesophase, which was identified by high-temperature X-ray diffraction as a smectic A phase. For the series from neodymium(III) pentanoate to neodymi um(III) undecanoate an additional high viscosity mesophase is present betwe en the crystalline state and the smectic A mesophase.