1-Dimensional and 2-dimensional coordination network structures in the Ba-Ce-dipicH < inf > 2 < /inf > system (dipicH < inf > 2 < /inf > = dipicolinic acid)

Abstract

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(dipicH2)(OH2)4Ce(dipic)3· 4.6H2O (1) is built up of 1-D alternating chains of nine-coordinate Ce and Ba polyhedra, each having tricapped trigonal prismatic geometry. The structure of Ba(OH2)6Ce(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)32- anions, is analogous to that of SrCl2·6H2O· Ba(OH2) 4Ce(dipic)3·2H2O (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. © 2005 Elsevier Ltd. All rights reserved.