Synthesis, Crystal Structure and Optical Properties of a Cerium(Ⅳ) Complex with Chelidamic Acid

A new cerium complex,(C7H8)Ce(C7H3NO5)2(H2O)3]·2H2O or (C7H8)Ce(HChel)2-(H2O)3]·2H2O (1,H3Chel = 4-hydroxypyridine-2,6-dicarboxylic (chelidamic) acid),has been prepared by the hydrothermal reaction,and its crystal structure was determined based on single-crystal diffraction data. Compound 1 crystallizes in monoclinic,space group P21/c with a = 12.4267(9),b = 10.8195(7),c = 19.5650(13),β = 92.898(3)o,V = 2627.2(3) 3,Dc = 1.733 g/cm3,Z = 4,Mr = 685.55,μ = 1.809 mm-1,λ(MoKα) = 0.71073  and F(000) = 1372. The final R = 0.0455 and wR = 0.1984 for 5983 observed reflections with Ⅰ > 2σ(Ⅰ),and R = 0.0490 and wR = 0.2053 for all data. Complex 1 contains one cerium ion,two chelidamic acid ligands,three coordinated water molecules,one discrete toluene molecule,and two discrete water molecules. The Ce(IV) ion is nine-coordinate with the coordination polyhedron made up of four oxygen atoms and two nitrogen atoms from two tridentate chelating chelidamic acid ligands,and three coordinated water molecules. A three-dimensional network is formed by the H-bonds. Moreover,optical properties are investigated and the results show that this complex has sharp optical absorption at 221,396 and 571 nm but no marked fluorescent emission.