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 three-dimensional 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 ·6 DMF], -50 [Nd 2 (NDC) 3 O(DMF) 2 ], -51 [Eu 2 (NDC) 3 (DMF) 2 ·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%. We report four lanthanide metal-organic frameworks based on 2,6-naphthalenedicarboxylate which displays multiple bonding modes, implying more structures await discovery.