A Series of Four-Connected Entangled Metal-Organic Frameworks Assembled from Pamoic Acid and Pyridine-Containing Ligands: Interpenetrating, Self-Penetrating, and Supramolecular Isomerism

Five novel compounds, {[Ni(FA)(bpe)(H2O2]center dot DMF}(n) (1), {[Zn(FA)center dot(bpe)]center dot DMF}(n) (2), {[Zn(FA)(bpe)]center dot 2DMF center dot CH3OH}(n) (3), {[Cd-2(PA)(2)(bPe)(2)(H2O)]center dot 3.5H(2)O}(n) (4), {[Ni-2(PA)(2)(bPP)(2)(H2O)(3)]center dot 2DMF}(n) (5), based on pamoic acid (H(2)PA) (bpe = 1,2-bi(4-pyridyl)ethane, bpp = 1,3-bi(4-pyridyl)propane) have been synthesized. In such a system, both the PA(2-) anion ligand and dipyridyl ligands act as bipodal linkers, connecting the metal centers in square or tetrahedral geometries into 4-connected topologies with different entangled modes: 3-fold interpenetrating CdSO4 net (6(s).8) (1), roto-translational [2 + 2] interpenetrating diamond pseudosupramolecular isomers (2 and 3), 3-fold interpenetrating (6.7(4).8)(6(4).7.8) (4) and (6.8(s)) (6(4).8(2)) net with both 2-fold interpenetrating and self-penetrating characters (5), respectively. The formation of unique penetrating frameworks was investigated in detail. Gas adsorption and photoluminescent properties of the compounds have also been explored.