Charge transfer adducts of binuclear rare earth 3,5-dinitrobenzoates with N,N-dimethylaniline and toluene

Abstract

Crystallization of the products of an exchange between LnCl3·6H2O and potassium 3,5-dinitrobenzoate from N,N-dimethylaniline (DMA) in the presence of DMSO afforded the isostructural complexes [Ln2(O2CC6H3(NO2)2)6(DMSO)4]·3(Me2N)C6H5 (where Ln=Eu (1 and its polymorphic modification 1a), Gd (2), Tb (3), Dy (4) and Y (5)). In addition, formation of the metastable compounds [Tb2(O2CC6H3(NO2)2)6(DMSO)4]·5(Me2N)C6H5 (3a) and [Ln2(O2CC6H3(NO2)2)6(DMSO)4]·4(Me2N)C6H5 (Ln=Eu (1b), Tb (3b), Dy (4a), Y (5a)) was found. Due to charge transfer (CT), the stacking interactions between DMA molecules and 3,5-dinitrobenzoate moieties occur, which determine the supramolecular structure of compounds 1–5. The CT also determines the weak paramagnetism of the Y compound, but its effect on the overall magnetism of the compounds is insignificant. The structure and physicochemical properties of compounds 1–5 are considered in comparison with those of the newly synthesized complexes [Eu2(O2CC6H3(NO2)2)6(DMSO)4]·2.2MePh⋅0.8DMSO (6), [Ln2(O2CC6H3(NO2)2)6(DMSO)4]·3MePh (Ln=Gd (7), Tb (8)), [Dy2(O2CC6H3(NO2)2)6(DMSO)4]·2MePh·DMSO (9), and [Y2(O2CC6H3(NO2)2)6(DMSO)4]·2.52MePh·0.48DMSO (10), in which CT is minor. For compound 2, a correlation between the heat capacity and magnetic behavior is found. Gadolinium complexes 2 and 7 are found to have weak ferromagnetic interactions between the Gd3+ ions. Complex 9 displays the properties of a single molecule magnet. For compound 2, standard thermodynamic functions were calculated.