A New Ferrimagnet Based on a Radical-Substituted Radical Cation Salt

Abstract

Radical-substituted radical cations are attractive spin building blocks of molecule-based magnets. The introduction of an additional spin as a counteranion provides a unique three-spin system wherein the magnetic interactions between the spins of the radical substituent and the radical cation (J(intra)) and those between the spins of the radical cation and the anion (J(inter)) play decisive roles in determining the magnetic properties of the system. We report the first demonstration of a ferrimagnet by utilizing a large-J(intra) system, nitronyl nitroxide-substituted dihydrophenazine radical cation (NNDPP(*+)) in combination with tetrabromoferrate (FeBr(4)(-)) as the counteranion. On the basis of measurements of dc and ac magnetic susceptibilities and heat capacity, the magnetic properties of NNDPP(*+) x FeBr(4)(-) are elucidated to be those of a three-dimensional long-range-ordered ferrimagnet with T(c) = 6.7 K.

2-[2-(2-Hydroxyethoxy)phenyl]-4,4,5,5-tetramethyl-2-imidazoline-1-oxyl 3-oxide

“…For their coordination properties, see: Masuda et al (2009). For puckering parameters, see : Cremer & Pople (1975).…”

2-[4-(2-Hydroxyethoxy)phenyl]-4,4,5,5-tetramethyl-2-imidazoline-1-oxyl 3-oxide

“…For biological properties of nitronyl nitroxides, see: Soule et al (2007); Blasig et al (2002); Qin et al (2009); Tanaka et al (2007). For coordination properties of nitronyl nitroxides, see: Masuda et al (2009). For related structures, see: ; Jing et al (2009).…”

2-(1H-Indol-3-yl)-4,4,5,5-tetramethylimidazolidine-1-oxyl 3-oxide

“…For the preparation of nitronyl nitroxides, see: Ullman et al (1974). For their biological activity, see: Soule et al (2007) and their coordination properties, see: Masuda et al (2009). For related structures, see: Iqbal et al (2009); Qin et al (2009); Tanaka et al (2007).…”

“…Nitronyl nitroxides, stable organic radicals, that were originally synthesized more than 30 years ago (Ullman et al1974), have recently received considerable attention (Iqbal et al 2009;Qin et al 2009;Tanaka et al 2007) because of their biological properities as anticancer, antiradiation and antioxidation (Soule et al, 2007). The title compound itself can be used to form coordination compounds with many metal cations, such as Mn 2+ , Cu 2+ and Ni 2+ leading to some interesting magentic materials (Masuda, et al, 2009). The molecular structure of the title compound is shown in (Table 1).…”