J. Phys. IV France 114 (2004) 651
Magnetism in organic radical ion salts based on imidazolyl and benzimidazolyl nitronyl nitroxideT. 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
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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) and (2-BIMNN) 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 K for Li +(2-IMNN) and K for (2-IMNN) Cl -, indicating weak interactions. The diradical cation salt (2,6-PYBNN) Cl - shows intramolecular ferromagnetic interaction with J/k = +4.7 K and intermolecular antiferromagnetic interaction with 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.
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