1-Dimensional and 2-dimensional coordination network structures in the Ba-Ce-dipicH2 system (dipicH2 = dipicolinic acid)

Reaction of dipicolinic acid with ammonium ceric nitrate and barium chloride produces, by self-assembly, three coordination polymers having similar stoichiometry but very different network structures. The structure of Ba(dipicH(2))(OH2)(4)Ce(diPiO)(3) center dot 4.6H(2)O (1) is built up of 1-D alternating chains of nine-coordinate Cc and Ba polyhedra, each having tricapped trigonal prismatic geometry. The structure of Ba(OH2)(6)Ce(diPiC)(3) (2), wherein a chain of nine-coordinate aquo-Ba polyhedra is threaded through the channel formed by a trigonal arrangement of the Ce(dipic)(3)(2-) anions, is analogous to that of SrCl2 center dot 6H(2)O center dot Ba(OH2)(4)Ce(diPiC)(3) center dot 2H(2)O (3), a polymorph of 2 (formally its hydrate isomer), exhibits a layered network in which Ce and Ba coordination polyhedra are linked by dipic ligands to form a corrugated sheet structure and may be considered as a metal-organic analog of the PbO lattice. (c) 2005 Elsevier Ltd. All rights reserved.