Antiferromagnetic Porous Metal–Organic Framework Containing Mixed-Valence [MnII 4MnIII 2(μ4-O)2]10+ Units with Catecholase Activity and Selective Gas Adsorption

A multifunctional porous metal organic framework based on mixed-valence hexa-nuclear [MnIII 2MnII 4O2(pyz)2(C6H5CH2COO)10] (pyz = pyrazine) units has been synthesized. The complex has been characterized by elemental analysis, IR spectroscopy, single-crystal X-ray diffraction analysis, and variable-temperature magnetic measurements. The structural analysis reveals that the bidentate pyz molecules connect each [Mn6] unit to its four [Mn6] neighbors through the peripheral Mn(II) centers, giving rise to a three-dimensional (3D) distorted diamond-like porous framework. Variable-temperature (2–300 K) magnetic susceptibility measurements show the presence of dominant antiferromagnetic interactions within the discrete [Mn6] cluster that have been fitted with a model containing three exchange constants developed for the complex (J 1 = −8.6 cm–1, J 2 = −3.9 cm–1, and J 3 = −100.0 cm–1). Using 3,5-di-tert-butyl catechol (3,5-DTBC) as the substrate, catecholase activity of the complex has been studied; the turn over number is determined to be of 2547 h–1 in acetonitrile. This porous compound shows remarkable selectivity for adsorption of CO2 over N2 that may be correlated with the effect of window flexibility of the pore to the corresponding adsorbate molecules.