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), [Ln(2)(pam)(3)(DMF)(2)(H2O)(2)](n). nDMF {Ln = Gd(1), Dy(2); H(2)pam = 4,4'-methylenebis[3-hydroxy-2-naphthalenecarboxylic acid]} using the pharmaceutical agent pamoic acid (H(2)pam) 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 X 15.163 angstrom (for 1) and 14.58 X 17.23 angstrom (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, -Delta S-m, of 17.25 J kg(-1) K-1(Delta H = 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 cm(3) g(-1) for 1 and 201 cm(3) g(-1) for 2). Solid state photoluminescence properties reveal that they are photoluminescent materials.