Synthesis and Characterization of Two Lanthanide (Gd3+ and Dy3+)‑Based Three-Dimensional Metal Organic Frameworks with Squashed Metallomacrocycle Type Building Blocks and Their Magnetic, Sorption, and Fluorescence Properties Study

Two novel isostructural lanthanide- based three-dimensional (3D) metal organic frameworks (MOFs), [Ln2(pam)3(DMF)2(H2O)2]n·nDMF {Ln = Gd­(1), Dy­(2); H2pam = 4,4′-methylenebis­[3-hydroxy-2-naphthalenecarboxylic acid]} using the pharmaceutical agent “pamoic acid (H2pam)” are synthesized for the first time. Single crystal structure analysis shows that the 3D framework originates from the self-assembly of lanthanide metallomacrocycles made of dumble-shaped basic secondary building units and having channels of sizes 17.427 × 15.163 Å (for 1) and 14.58 × 17.23 Å (for 2), respectively. In both the complexes, two eight-coordinated lanthanide centers are connected with six pamoate groups to give a paddle-wheel type building block. The arrangement of pamoates and lanthanides in the framework provokes both right- (P) and left-hand (M) helicity around the 21 screw axis. The magnetic measurements show that complex 1 acts as a cryogenic magnetic refrigerant having magnetic entropy change, −ΔSm, of 17.25 J kg–1 K–1(ΔH = 7 T at 3 K), and complex 2 shows slow relaxation of magnetization. The adsorption studies reveal that complexes 1 and 2 show selectivity toward CO2 sorption over other gases and exhibit high methanol vapor uptake (227 cm3 g–1 for 1 and 201 cm3 g–1 for 2). Solid state photoluminescence properties reveal that they are photoluminescent materials.