A Series of Metal-Organic Frameworks with 2,2'-Bipyridyl Derivatives: Synthesis vs. Structure Relationships, Adsorption, and Magnetic Studies.

Five new metal-organic frameworks based on Mn(II) and 2,2'-bithiophen-5,5'-dicarboxylate (btdc) with various chelating N-donor ligands (2,2'-bipyridyl = bpy; 5,5'-dimethyl-2,2'-bipyridyl = 5,5'-dmbpy; 4,4'-dimethyl-2,2'-bipyridyl = 4,4'-dmbpy) [Mn(btdc)(bpy)]·4DMF, ; [Mn(btdc)(5,5'-dmbpy)]·5DMF, ; [Mn(btdc)(4,4;-dmbpy)], ; [Mn(btdc)(bpy)(dmf)]·0.5DMF, ; [Mn(btdc)(5,5'-dmbpy)(dmf)]·DMF, (dmf, DMF = N,N-dimethylformamide) have been synthesized, and their crystal structure has been established using single-crystal X-ray diffraction analysis (XRD). The chemical and phase purities of Compounds - have been confirmed via powder X-ray diffraction, thermogravimetric, and chemical analyses as well as IR spectroscopy. The influence of the bulkiness of the chelating N-donor ligand on the dimensionality and structure of the coordination polymer has been analyzed, and the decrease in the framework dimensionality, as well as the secondary building unit's nuclearity and connectivity, has been observed for bulkier ligands. For three-dimensional (3D) coordination polymer , the textural and gas adsorption properties have been studied, revealing noticeable ideal adsorbed solution theory (IAST) CO/N and CO/CO selectivity factors (31.0 at 273 K and 19.1 at 298 K and 25.7 at 273 K and 17.0 at 298 K, respectively, for the equimolar composition and the total pressure of 1 bar). Moreover, significant adsorption selectivity for binary C-C hydrocarbons mixtures (33.4 and 24.9 for CH/CH, 24.8 and 17.7 for CH/CH, 29.3 and 19.1 for CH/CH at 273 K and 298 K, respectively, for the equimolar composition and the total pressure of 1 bar) has been observed, making it possible to separate on natural, shale, and associated petroleum gas into valuable individual components. The ability of Compound to separate benzene and cyclohexane in a vapor phase has also been analyzed based on the adsorption isotherms of individual components measured at 298 K. The preferable adsorption of CH over CH by at high vapor pressures (/ = 1.36) can be explained by the existence of multiple van der Waals interactions between guest benzene molecules and the metal-organic host revealed by the XRD analysis of immersed in pure benzene for several days (). Interestingly, at low vapor pressures, an inversed behavior of with preferable adsorption of CH over CH (/ = 6.33) was observed; this is a very rare phenomenon. Moreover, magnetic properties (the temperature-dependent molar magnetic susceptibility, χ() and effective magnetic moments, μ(), as well as the field-dependent magnetization, ()) have been studied for Compounds -, revealing paramagnetic behavior consistent with their crystal structure.