J. Phys. I France 6 (1996) 1967-1986
Organic Ferromagnets. Hydrogen Bonded Supramolecular Magnetic Organizations Derived from Hydroxylated Phenyl -Nitronyl Nitroxide RadicalsJ. Veciana1, J. Cirujeda1, C. Rovira1, E. Molins1 and J.J. Novoa2
1 Institut de Ciència de Materials de Barcelona, CSIC, Campus de la U.A.B., 08193-Bellaterra, Catalunya, Spain
2 Departament de Química Física, Facultat de Química, Universitat de Barcelona, Av. Diagonal 647, 08028-Barcelona, Spain
(Received 30 April 1996, accepted 1 July 1996)
The capacity of hydrogen bonds as crystalline design elements for the preparation of solid state supramolecular organizations with relevant magnetic properties is reviewed. It will be shown here that hydrogen bonds fulfill two distinct purposes. One function is a structural one through which is possible to control up to certain level the relative arrangements of radical molecules. The other role of hydrogen bonds is a magnetic one since these bonds introduce proper pathways for the transmission of intermolecular magnetic interactions. Using this methodological approach several molecular magnetic solids have been prepared with hydroxylated phenyl -nitronyl nitroxide radicals. These molecular solids are formed by supramolecular motifs (dimers, chains, and planes) bonded by strong hydrogen bonds which are linked to each other by other weak forces that form the rest of the crystals. Consequently, the solids show different structural dimensionalities that in some cases do not agree with the magnetic ones. Accordingly with such distinct structural and magnetic dimensionalities, the resulting molecular solids show a wide variety of magnetic behaviors. Remarkable are the purely organic 2-D and 3-D ferromagnets reported here. Finally, the most relevant mechanisms explaining intermolecular magnetic interactions as well as the most promising applications expected for purely organic magnets are also included.
© Les Editions de Physique 1996