Ferromagnetic interactions in Ru( iii )–nitronyl nitroxide radical complex: a potential 2p4d building block for molecular magnets

The reaction between [Ru(salen)(PPh3)Cl] and the 4-pyridyl-substituted nitronyl nitroxide radical (NITpPy) leads to the [Ru(salen)(PPh3)(NITpPy)](ClO4)(H2O)2 complex while the reaction with the azido anion (N3-) leads to the [Ru(salen)(PPh3)(N3)] complex 2 (where salen2- = N,N'-ethan-1,2-diylbis(salicylidenamine) and PPh3 = triphenylphosphine). Both compounds have been characterized by single crystal X-ray diffraction. The two crystal structures are composed by a [Ru(III)(salen)(PPh3)]+ unit where the Ru(III) ion is coordinated to a salen2- ligand and one PPh3 ligand in axial position. In 1 the Ru(III) ion is coordinated to the 4-pyridyl-substituted nitronyl nitroxide radical whereas in 2 the second axial position is occupied by the azido ligand. In both complexes the Ru(III) ions are in the same environment RuO2N3P, in a tetragonally elongated octhaedral geometry. The crystal packing of 1 reveals pi-stacking in pairs. While antiferromagnetic intermolecular interaction (J2 = 5.0 cm(-1)) dominates at low temperatures, ferromagnetic intramolecular interaction (J1 = -9.0 cm(-1)) have been found between the Ru(III) ion and the coordinated NITpPy.