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(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 ) 3 2 - 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.