No abstract

Lanthanide and actinide based coordination polymers and metal-organic framework materials present a number of interesting opportunities with respect to their syntheses and properties. Ln elements typically display large coordination numbers and roughly spherical bonding environments whereas An elements (specifically U(VI)) tend to form triatomic species with terminal oxo groups. As such, these features may be perceived by some as obstacles to the development of designed architectures of f-metal containing hybrid materials. We argue that these features, when coupled to the luminescent behavior of these elements actually give rise to a diverse family of compounds with a range of interesting topologies. Presented herein is an overview of the structural features and luminescent behavior of these materials, as well as some synthetic strategies toward producing both homo-and heterometallic compounds.

Two lanthanide-organic frameworks were synthesized via hydrothermal methods. Compound 1 ([(Eu,Tb)(C6H8O4)3(H2O)2].(C10H8N2), orthorhombic, Pbcn, a = 21.925(2) A, b = 7.6493(7) A, c = 19.6691(15) A, alpha = beta = gamma = 90 degrees, Z = 4) takes advantage of the similar ionic radii of the lanthanide elements to induce a mixed-lanthanide composition. Compound 2 ([Tb2(C6H8O4)3(H2O)2].(C10H8N2), orthorhombic, Pbcn, a = 21.866(3) A, b = 7.6101(10) A, c = 19.646(3) A, alpha = beta = gamma = 90 degrees, Z = 8) is the terbium-only analogue of compound 1. Solid-state measurements of their luminescence behavior demonstrate that the neutral guest molecule (4,4'-dipyridyl) residing in the extraframework channels is successful in sensitizing lanthanide ion emission. In compound 1, columinescence occurs, and both lanthanide ions show emission. Additionally, quantum yield and lifetime measurements support the premise that the Tb3+ center is also acting to sensitize the Eu3+, effectively enhancing Eu3+ emission.