Magnetic and optical properties of nitroxide radicals and their lanthanide complexes

This paper reports the structural, magnetic and optical properties of three series of lanthanide complexes [Ln(radical)(4)](ClO4)(3), [Ln(radical)(2)(NO3)(3)] and [Ln(radical)(hfac)(3)] (Ln = Gd(III), La(III) or Eu(III)) with nitronyl or imino nitroxide radicals. The magnetic properties of the gadolinium complexes were studied. Along the series, most gadolinium(III) complexes exhibit antiferromagnetic Gd-III-radical interaction. These results are discussed. The full absorption and luminescence spectra of some lanthanide complexes and their,uncoordinated free radical ligands were measured. The rich vibronic structure in luminescence and absorption spectra indicates that several excited states define the absorption spectra between 400 and 800 nm. Qualitative trends can be established between magnetic ground state properties and the energies and vibronic structure of the title compounds. (C) 2003 Elsevier Ltd. All rights reserved.