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(PA)(bpe)(H 2 O) 2 ]·DMF} n ( 1 ), {[Zn(PA)(bpe)]·DMF} n ( 2 ), {[Zn(PA)(bpe)]·2DMF·CH 3 OH} n ( 3 ), {[Cd 2 (PA) 2 (bpe) 2 (H 2 O)]·3.5H 2 O} n ( 4 ), {[Ni 2 (PA) 2 (bpp) 2 (H 2 O) 3 ]·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 CdSO 4 net (6 5 .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 5 )(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.