Homometallic uranium(VI) phosphonoacetates containing interlayer dipyridines.

Three organically templated uranium(VI) carboxyphosphonates, [C(10)H(10)N(2)][(UO(2))(3)(PPA)(2)(HPPA)(H(2)O)] x 3 H(2)O (1), [C(12)H(12)N(2)][(UO(2))(3)(PPA)(2)(HPPA)(H(2)O)] x 2 H(2)O (2), and [C(12)H(14)N(2)][(UO(2))(3)(PPA)(2)(HPPA)(H(2)O)] x 2 H(2)O (3) have been prepared from hydrothermal reactions of UO(2)(NO(3))(2) x 6 H(2)O and phosphonoacetic acid (H(2)O(3)PCH(2)CO(2)H, H(3)PPA) in the presence of 4,4'-dipyridyl, 1,2-bis(4-pyridyl)-ethylene and 1,2-bis(4-pyridyl)-ethane. The crystal structures of 1-3 are built from UO(7) units linked via phosphonoacetate molecules to form 2-dimensional [(UO(2))(3)(PPA)(2)(HPPA)(H(2)O)](2-) networks which are charge balanced by doubly protonated bipyridyl molecules. Interaction of the pyridyl molecules with other functionalities present in 1-3 result in relatively strong N-H...O (2.707-3.155 A) and weaker C-H...O (2.948-3.237 A) interactions that constitute the interlayer. Water-carboxylate O-H...O hydrogen bonding (2.548-2.675 A) in 1-3 and pi-pi interactions (3.708 A) between pyridyl rings in 2 also exist in these materials. Reported herein are the syntheses, structural characterization, and thermal and fluorescent behavior of 1-3.