Variability of Uranyl Carboxylates from Rigid Terophenyldicarboxylic Acid Ligands

Three uranyl carboxylates, namely, (UO2)­(L1)­(H2O)0.5 (1), [(UO2)­(L2)­(H2O)]·2H2O (2), and [(UO2)­(L2)­(H2O)]·(CH3CN) (3), were synthesized hydrothermally from 2′,3′,5′,6′-tetramethyl-(1,1′:4′,1″-terphenyl)-4,4″-dicarboxylic acid (H2L1) and 2′,5′-dimethyl-(1,1′:4′,1″-terphenyl)-3,3″-dicarboxylic acid (H2L2), which are all steric carboxylic acid ligands but vary with the carboxylic acid group position and methyl group number. It is found that compound 1 displays a three-dimensional 8-fold-interpenetrated net with channels running along the c direction. Compounds 2 and 3 are isostructural, and all display two-dimensional-layered crystal structures but contain different guest molecules. The photophysical measurements reveal that compounds 1 and 2, which contain disordered water molecules, are luminescence-quenched, whereas compound 3 containing acetonitrile molecules is luminescent.