New butane-1,2,3,4-tetracarboxylato bridged cobalt(II) complexes

Four butane-1,2,3,4-tetracarboxylato bridged supramolecular complexes [Co2(H2O)5(BTC)]·2H2O 1, [Co2(H2O)5(BTC)]·2H2O 2, [Co2(H2O)6(bpy)2(BTC)]·4H2O 3 and [Co2(H2O)2(bpy)2(BTC)] 4, (H4BTC = butane-1,2,3,4-tetracarboxylic acid, 2,2-bpy = 2,2-bipydine) are synthesized and characterized by single-crystal X-ray diffraction. IR spectroscopy, TG-DTA analyses, elemental analyses, powder X-ray diffraction and magnetic measurements for 3 and 4 are carried out. The dinuclear Co unit in 2 is bridged by BTC4− anions into 2D layers, which are assembled via interlayer hydrogen bonds into a 3D (44·62)(45·65)2(46·68·8) topological supramolecular architecture. In 3, the [Co2(H2O)6(bpy)2(BTC)] molecules are aggregated to 2D layers via π–π stacking interactions, the resulting layers are engaged in hydrogen bonding leading to a novel 3D supramolecular architecture with the schläfli symbol of (102.12)2(4.102)2(42.102.122). The Co atoms in 4 are linked by BTC4− anions into a 1D chain, then the hydrogen bonding and π–π stacking interactions result in formation of a 3D novel (43.62.8)2(46.66.83)(63)2 topological networks. The variable temperature magnetic characterizations on 3 and 4 suggest weak antiferromagnetic or ferromagnetic coupling exchange via π···π stacking interactions (J = –0.03 cm−1 for 3, J = 0.11 cm−1 for 4).