J. Phys. IV France
Volume 114, April 2004
Page(s) 651 - 653

J. Phys. IV France
114 (2004) 651
DOI: 10.1051/jp4:2004114157

Magnetism in organic radical ion salts based on imidazolyl and benzimidazolyl nitronyl nitroxide

T. Sugano1, 1, S.J. Blundell2, W. Hayes2 and P. Day3

1  Department of Chemistry, Meiji Gakuin University, Kamikurata, Totsuka, Yokohama 244-8539, Japan
2  Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford OX1 3PU, UK
3  Royal Institution of Great Britain, 21 Albemarle Street, London W1S 4BS, UK

Radical ion salts of the neutral organic radicals, 2-imidazolyl nitronyl nitroxide (2-IMNN) and 2-benz- imidazolyl nitronyl nitroxide (2-BIMNN), and a diradical cation salt of pyridine-2,6-diylbis(nitronyl nitroxide) (2,6-PYBNN), were prepared. The radical ion salts of 2-BIMNN, Li +(2-BIMNN) $^{\bullet -}$ and (2-BIMNN) $^{\bullet
+}$ BF 4-, exhibit strong antiferromagnetic interactions with exchange coupling constants J/k = -42 K and -510 K, respectively, while the 2-IMNN salts show Curie-Weiss behaviour with Weiss constants $\theta = -9.0$ K for Li +(2-IMNN) $^{\bullet -}$ and $\theta = -1.8$ K for (2-IMNN) $^{\bullet
+}$ Cl -, indicating weak interactions. The diradical cation salt (2,6-PYBNN) $^{\bullet \bullet +}$Cl - shows intramolecular ferromagnetic interaction with J/k = +4.7 K and intermolecular antiferromagnetic interaction with $\theta = -0.7$ K, which is remarkably reduced from J/k = -57 K observed in the diradical 2,6-PYBNN. Key words. Magnetism - molecular compounds - radical ion salts.

© EDP Sciences 2004