Structural Characterization, Water Adsorption, and Magnetic Properties of Two Composite Mn(II)-Squarate-dpe Supramolecular Architectures

Two supramolecular architectures, [Mn(Hdpe)-(C4O4)(0.5)(H2O)(3)][Mn-(C4O4)(2)(H2O)(2)] (1) and [Mn-(Hdpe)(2)(H2O)(4)][Mn-(C4O4)(2)(H2O)(2)](2)center dot 8H(2)O (2) (C4O42- = dianion of squaric acid (H2C4O4); dpe = 1,2-bis(4-pyridyl)ethane), have been synthesized in one-pot reactions and structurally characterized by single-crystal X-ray diffraction methods. Compounds 1 and 2 are both 2D coordination polymers with interdigitated layers, constructed by two two-dimensional (2D) anionic [Mn(mu(1,3)-C4O4)(2) (H2O)(2)](2-) layered metal-organic frameworks (MOFs) with their open square-grid windows penetrated by the anti-Hdpe(+) ligands of the, cationic [Mn (Hdpe) (mu(1,2,3,4)- C4O4)(0.5)(H2O)(3)](2+) layered MOF in 1 and the cationic [Mn(Hdpe)(2)(H2O)(4)](4+) monomers in 2, to generate 2D trilayered and 2D bilayered frameworks, respectively. Both of them are then extended to 3D supramolecular architectures via strong intermolecular interactions, including hydrogen bonds and pi-pi stacking interactions, among the neighboring 2D frameworks. Compounds 1 and 2 exhibit significant water vapor hysteresis isotherms, and their cyclic water de-/adsorption behavior accompanied by a structural transformation has been verified by TG analyses and PXRD measurements through de-/rehydration processes. The magnetic properties of 1 and 2 suggest that the weak antiferromagnetic behavior is related to the weak inter-Mn(II) interactions via C4O42- bridges in the 2D frameworks.