Crystal structures and magnetic properties of two complexes synthesized from manganese and halogenophenyl-substituted nitronyl nitroxide

One-dimensional complex (1), [Mn(hfac)₂(NITPhF)]₂ and one binuclear radical complex (2), [Mn(hfac)₂(NITPhBr)]_∞ have been synthesized. Here hfac stands for hexafluoroacetylacetonate, NITPhF for 2-(4′-fluorophenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, and NITPhBr for 2-(4′-bromophenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide). All the two precursors were prepared and characterized by single-crystal X-ray diffraction analysis, IR, and magnetic analysis. In complex 1, the NITPhF radical acts as a bridge ligand linking two Mn(II) ions through the oxygen atom of the N-O group to form cyclic dimer. The dimers further connect two oxygen atoms of uncoordinated nitroxides of two adjacent radicals and yield one-dimensional chain sections. Instead in complex 2, the Mn(II) ions are bridged by the NITPhBr radicals through their N-O groups giving infinite one-dimensional chains. Magnetic susceptibility measurements indicate that both complex 1 and 2 behave ferrimagnetically. The Mn(II) ions interact antiferromagnetically with the direct bonding nitroxide group of the radicals although the structures of two complexes are different. The magnetic behaviors can be satisfactorily explained on the basis of the structural data.