Hybrid organic-inorganic layered compounds prepared by anion exchange reaction: correlation between structure and magnetic properties

The synthesis, structure and magnetic properties of a series of hybrid organic-inorganic copper(II) compounds are reported. Anion exchange reactions were used to prepare layered materials made of copper(II)-based inorganic layers separated by long chain anions (n-alkyl sulfates or n-alkyl carboxylates). Contrary to classical intercalated compounds, the exchanged anion is coordinated to the metal ion. Different packing modes of the n-alkyl chains (mono- or bi-layers) are evidenced, depending on the bridging functions. The magnetic properties have been related to the nature of the anionic spacer and the basal spacing. When ferromagnetic in-plane interactions dominate, 3D ferromagnetic ordering is usually observed for large spacing, due to a dipolar coupling effect. For unsaturated aliphatic chains, pi electrons are shown to reinforce the interlayer exchange coupling, giving a ferromagnetic groundstate.