Magnetic and Structural Studies into the Effect of Solvent Exchange Process in Metal-Organic Framework MOF-76(Gd)

Effect of solvent exchange/absence on magnetic and structural properties of microporous metal-organic framework MOF-76(Gd) has been performed. Three compounds have been prepared and characterized: as synthesized MOF-76(Gd)-DMF, which containing DMF (N, N'-dimethylformamide) and H2O molecules in the cavity system, activated complex without solvents, MOF-76(Gd) and water exchanged sample MOF-76(Gd)-H2O. The structural study showed that compounds undergo structural changes after activation/exchange processes. Changes were mainly observed in the magnetic properties and distances between Gd center dot center dot center dot Gd ions: 4.718 angstrom for MOF-76(Gd)-DMF, 4.326 angstrom for MOF-76(Gd)-H2O and 4.296 angstrom for MOF-76(Gd). The magnetic properties of the samples were studied by magnetic susceptibility chi(M)(T) and magnetization M(H). The low positive value of the Weiss constant, Theta = 1.54 K in compound MOF-76(Gd)-DMF shows on a very weak ferromagnetic interaction. On the contrary, the negative values of Theta in complexes MOF-76(Gd) (-5.58 K) and MOF-76(Gd)-H2O (-6.23 K) confirm the existence of antiferromagnetic exchange interaction between Gd(III) ions.