SYNTHESIS AND MAGNETIC-BEHAVIOR OF RARE-EARTH COMPLEXES WITH N,O-CHELATING NITRONYL NITROXIDE TRIAZOLE LIGANDS - EXAMPLE OF A [GD-III(ORGANIC RADICAL)(2)] COMPOUND WITH AN S=9 2 GROUND-STATE/

Paramagnetic metal complexes that display a total spin ground state hi gher than that of the metal ion alone are interesting building blocks for the construction of molecular magnetic materials, Here we describe the synthesis and the magnetic properties of three such lanthanide co mplexes with two organic radicals as ligands, [Ln(nittrz)(2)(NO3)(3)], where Ln = Y, La, or Gd and nittrz is a nitronyl nitroxide substitute d triazole derivative interacting as an eta(2)-N,O chelate to the meta l center. For the Gd-III derivative a ferromagnetic exchange interacti on [J = 6.1 cm(-1), H = -J (S) over cap(Gd)((S) over cap(rad1) + (S) o ver cap(rad2))] occurs between the paramagnetic metal center (S-Gd = 7 /2) and the ligands (S-rad1 = S-rad2 = 1/2) that gives rise to an S = 9/2 ground state. The molecular structure of this compound has been de termined by X-ray diffraction.