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

T. Sugano; S.J. Blundell; W. Hayes; P. Day

doi:doi:10.1051/jp4:2004114157

Numéro		J. Phys. IV France Volume 114, April 2004


Page(s)		651 - 653
DOI		https://doi.org/10.1051/jp4:2004114157

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. Sugano^{1, 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
e-mail: stephen.blundell@mansfield.oxford.ac.uk; w.hayes1@physics.ox.ac.uk
³ Royal Institution of Great Britain, 21 Albemarle Street, London W1S 4BS, UK
e-mail: profpday@msn.com

Abstract
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.