Copper(II) coordination frameworks with 1H-benzimidazole-5,6-dicarboxylic acid: syntheses,crystal structures and magnetic properties

Cu(II) polymers of Hbidc (1H-benzimidazole-5,6-dicarboxylate), namely [Cu₂(Hbidc)₂(H₂O)₄·3H₂O] _n (1) and [Cu(Hbidc)] _n (2), were synthesized under hydrothermal conditions by variation of the reaction temperature and characterized by physico-chemical, spectroscopic and single-crystal X-ray diffraction studies. At temperatures from 100 to 170 °C, we only obtained the 2-D structure compounds 1 and 2, in which the bridging mode of the Hbidc ligand increases from μ ₃ to μ ₅ and the number of water ligands decreases to 0. Both compounds have 3-D supramolecular architectures extended by hydrogen bonding and π–π interactions between the adjacent layers. Magnetic studies revealed that compound 1 shows weak antiferromagnetic properties and compound 2 exhibits ferromagnetic coupling between the two Cu(II) ions in the dimeric units.