Syntheses, structures, luminescent and magnetic properties of a novel class of metal complexes constructed from 2-(2-pyridyl)benzimidazole and 5-hydroxy-1,3-benzenedicarboxylic acid

Four novel metal coordination polymers, [Zn(2-PBIM)(OH-BDC)]_n (1), [Cd(2-PBIM)(OH-BDC)]_n (2), [Mn(2-PBIM)(OH-BDC)]_n·1.5nH₂O (3), [Cu(2-PBIM)(OH-BDC)]_n·nH₂O (4) [2-PBIM = 2-(2-pyridyl)benzimidazole; OH-H₂BDC = 5-hydroxy-1,3-benzenedicarboxylic acid], have been synthesized under hydrothermal conditions and structurally characterized by single crystal X-ray diffraction analysis, elemental analysis, IR spectroscopy, and thermogravimetric analysis. Compound 1 possesses left-handed screw (M-helix) and right-handed screw (P-helix) chains that are further connected though intermolecular hydrogen bonds and π-π stacking interactions resulting in a three-dimensional (3D) network. Compound 2 has a two-dimensional metal-organic framework which is connected into a 3D network by intermolecular hydrogen bonds and π-π stacking interactions. Compounds 3 and 4 are isostructural and possess one-dimensional (1D) channels. Free 2-PBIM and OH-H₂BDC ligands and complexes 1, 2 show fluorescent emissions in the visible and near-infrared region. Magnetic susceptibility measurements indicate that both 3 and 4 exhibit antiferromagnetic coupling between adjacent center atoms.