Two New Coordination Polymers with Co(II) and Mn(II): Selective Gas Adsorption and Magnetic Studies

A novel bifurcated ligand 3,5-di­(1<i>H</i>-benzo­[<i>d</i>]­imidazol-1-yl)­benzonitrile (DBIBN) has been synthesized, which reacts with Co­(II) and Mn­(II) salts to form new coordination polymers {[Co₂(DBIBA)₃]·Cl·9H₂O}_<i>n</i> (<b>1</b>) and {[Mn₃(DBIBA)₆]}_<i>n</i> (<b>2</b>), (DBIBA = 3,5-di­(1<i>H</i>-benzo­[d]­imidazol-1-yl)­benzoate), in which DBIBN get hydrolyzed into DBIBA under solvothermal conditions. Both the complexes have been characterized by single-crystal X-ray crystallography (XRD), IR spectroscopy, elemental analysis, thermogravimetry, and X-ray powder diffraction (PXRD). Complex <b>1</b> is a 3D coordination polymer composed of binuclear Co­(II) units, having (4,6) connected net. On the other hand, complex <b>2</b> is a layered structure with trinuclear Mn­(II) units, which has 4-connected 4⁴ <i><b>sql</b></i> topology. TGA and PXRD measurements show that the framework <b>1</b> is stable after desolvation. Desolvated framework <b>1</b> showed selective adsorption of CO₂ over N₂, H_2, and Ar. Variable temperature magnetic susceptibility measurements show that complex <b>1</b> exhibits weak antiferromagnetic behavior