Luminescent lanthanide coordination polymers

One-dimensional lanthanide coordination polymers with the formula Ln(isonicotinate)(3)(H2O)(2) (Ln = Ce, Pr, Nd, Sm, Eu, Tb; la-f) were synthesized by treating nitrate or perchlorate salts of Ln(III) with 4-pyridinecarboxaldehyde under hydro(solvo)thermal conditions. Single-crystal and powder X-ray diffraction studies indicate that these lanthanide coordination polymers adopt two different structures. While Ce(III), Pr(III), and Nd(III) complexes adopt a chain structure with alternating Ln-(carboxylate)(2)-Ln and Ln-(carboxylate)(4)-Ln linkages, Sm(III), Eu(III), and Tb(III) complexes have a doubly carboxylate-bridged infinite-chain structure with one chelating carboxylate group on each metal center. In both structures, the lanthanide centers also bind to two water molecules to yield an eight-coordinate, square antiprismatic geometry. The pyridine nitrogen atoms of the isonicotinate groups do not coordinate to the metal centers in these lanthanide(III) complexes; instead, they direct the formation of Ln(III) coordination polymers via hydrogen bonding with coordinated water molecules. Photoluminescence measurements show that Tb(isonicotinate)(3)(H2O)(2) is highly emissive at room temperature with a quantum yield of similar to 90%. These results indicate that highly luminescent lanthanide coordination polymers can be assembled using a combination of coordination and hydrogen bonds. Crystal data for 1a: monoclinic space group P2(1/c), a = 9.712(2) Angstrom, b = 19.833(4) Angstrom,c = 11.616(2) Angstrom, beta = 111.89(3)degrees, Z = 4. Crystal data for 1f: monoclinic space group C2/c, a = 20.253(4) Angstrom, b = 11.584(2) Angstrom, c = 9.839(2) Angstrom, beta = 115.64(3)degrees, Z = 8.