Layered molecule-based magnets formed by decamethylmetallocenium cations and two-dimensional bimetallic complexes [M(II)Ru(III)(ox)3]-(M(II) = Mn, Fe, Co, Cu and Zn; ox = oxalate)

A new series of hybrid organometallic-inorganic layered magnets with formula [Z(III)Cp(2)(*)] [(MRuIII)-Ru-II(ox)(3)] (Z(III) = Co and Fe; M-II = Mn, Fe, Co, Cu, and Zn; ox = oxalate: Cp* = pentamethylcyclopentadienyl) has been prepared. All of these compounds are isostructural to the previously reported [Z(III)Cp(2)*] [(MMIII)-M-II(ox)(3)] (M-III = Cr, Fe) series and crystallize in the monoclinic space group C2/m, as found by powder X-ray diffraction analysis. They are novel examples of magnetic materials formed by bimetallic oxalate-based extended layers separated by layers of organometallic cations, The magnetic properties of all these compounds have been investigated (ac and de magnetic susceptibilities and field dependence of the isothermal magnetization at 2 K), In particular, it has been found that Fe-II and Co-II derivatives behave as magnets with ordering temperatures of 12.8 and 2.8 K, respectively, while no long-range magnetic ordering has been detected down to 2 K in the Mn-II and Cu-II derivatives. The magnetic ordering in the Fe-II derivatives has been confirmed through Mossbauer spectroscopy. This technique has also made it possible to observe the spin polarization of the paramagnetic [FeCp2*](+) units caused by the internal magnetic field created by the bimetallic layers in the ordered state. (C) 2001 Academic Press.