Supramolecular architecture of metal–organic frameworks involving dinuclear copper paddle-wheel complexes

Abstract
The two centrosymmetric dinuclear copper paddle-wheel complexes tetrakis(μ-4-hydroxybenzoato-κ2O:O′)bis[aquacopper(II)] dimethylformamide disolvate dihydrate, [Cu2(C7H5O3)4(H2O)2]·2C3H7NO·2H2O, (I), and tetrakis(μ-4-methoxybenzoato-κ2O:O′)bis[(dimethylformamide-κO)copper(II)], [Cu2(C8H7O3)4(C3H7NO)2], (II), crystallize with half of the dinuclear paddle-wheel cage unit in the asymmetric unit and, in addition, complex (I) has one dimethylformamide (DMF) and one water solvent molecule in the asymmetric unit. In both (I) and (II), two CuIIions are bridged by foursyn,syn-η1:η1:μ carboxylate groups, showing a paddle-wheel cage-type structure with a square-pyramidal coordination geometry. The equatorial positions of (I) and (II) are occupied by the carboxylate groups of 4-hydroxy- and 4-methoxybenzoate ligands, and the axial positions are occupied by aqua and DMF ligands, respectively. The three-dimensional supramolecular metal–organic framework of (I) consists of three differentR22(20) and anR44(36) ring motif formedviaO—H...O and OW—HW...O hydrogen bonds. Complex (II) simply packs as molecular species.