Intercalation of [M(ox)3]3- (M = Cr, Rh) complexes into NiIIFeIII-LDH

Layered Double Hydroxides (LDH) containing paramagnetic Ni-II and Fe-III ions in the hydroxide layers and chromium or rhodium oxalate complexes at the interlayer space were prepared by ion exchange from a NiFe-LDH precursor with sebacate anions between the hydroxide layers. The precursor was synthesized by coprecipitation at controlled pH in order to avoid the formation of solid phases different from LDH. Magnetic studies demonstrated that both LDHs, NiFe-Cr(ox)(3) and NiFe-Rh(ox)(3), exhibited a behaviour similar to the precursor. Nevertheless, the substitution of intercalated sebacate anions with oxalate complexes compresses the LDH basal spacing, increasing the intensity of dipolar interactions between the ferrimagnetic sheets, which promoted a small increment in the critical temperatures. With respect to variations of the magnetic properties between the oxalate intercalated materials, neither critical temperature nor coercive fields showed any remarkable difference. These systems though, represent the initial step in the design of new magnetic hybrid materials. (C) 2009 Elsevier B.V. All rights reserved.