Structural diversity of four lanthanide metal-organic frameworks based on 2,6-naphthalenedicarboxylate: synthesis, structures and photoluminescent properties

We report the crystal structures of four different neutral lanthanide (Ln = La, Nd, Eu and Gd) metal-organic frameworks based on the organic linker 2,6-naphthalenedicarboxylate (NDC). The materials are threedimensional and crystallize in three distinct topologies, with distinct bonding modes of NDC and lanthanide coordination numbers ranging from seven to nine and varying geometry. We denote our materials SLUG-49 [La-6(NDC)(9)(DMF)(3)center dot 6 DMFI, -50 [Nd-2(NDC)(3)O(DMF)(2)], -51 (Eu-2(NDC)(3)(DMF)(2)center dot DMF], and -52 [Gd-4(NDC)(6)(DMF)(4)] (DMF = N,N-dimethylformamide). The structures exhibit similar thermal decomposition profiles and infrared spectra. The Eu(III)-based material exhibits a sharp red-orange luminescence at 613 nm with a quantum efficiency of 3.56%.