Exploring the Slow Magnetic Relaxation of a Family of Photoluminescent 3D Lanthanide-Organic Frameworks Based on Dicarboxylate Ligands

A family of metal-organic frameworks with general formula {[Nd-2(ant)(2)((NH2)(2)-bdc)(DMF)(4)]center dot 2DMF}(n) (1) and {[Ln(2)(ant)(2)((NH2)(2)-bdc)(DMF)(4)]center dot 2DMF center dot 2H(2)O}(n) (Ln = Tb (2), Ho (3), and Er (4)) has been obtained from reactions between 9,10-anthracenedicarboxylic (H(2)ant) and 2,5-diaminoterephthalic ((NH2)(2)-H(2)bdc) acids, and lanthanide ions in dimethylformamide (DMF). These lanthanide-organic frameworks (LnOFs) have been characterized, and their crystal structures have been elucidated by single crystal and powder X-ray diffraction methods (on the basis of a comparative refinement with similar structures), respectively for 1 and 2-4. All LnOFs present three-dimensional structures composed of dinuclear [Ln(2)(mu-CO2)(4)] entities linked through both carboxylate ligands that yield open frameworks in which DMF and water molecules are located in the channels. Magnetic studies of these LnOFs have revealed slow relaxation of the magnetization for the Nd-based counterpart. The compounds also acknowledge relevant photoluminescence (PL) emissions in the visible (for the Tb-based homologue) and near-infrared (for the Nd- and Er-based compounds) regions. The strong green emission yielded by compound 2 at room temperature allows its study for photoluminescence (PL) sensing of various solvent molecules, finding a particular discrimination for acetone.