The First Metal Complex Involving an .alpha.-H-Containing Nitroxide

Abstract

On the basis of the 25-year studies on the synthesis of metal complexes with nitroxides, it was believed that nitroxides were kinetically stable during complex formation only if all substituents in the -position to the nitroxyl group were hydrocarbons.* 12 This concept was extended to the recent extensive investigations in the design of molecular ferromagnets based on metal complexes with stable nitroxides. Since in molecular ferromagnets the hydrocarbon substituents should be as small as possible, as is the case with methyl groups, the number of stable nitroxides employed at present in the design of molecular ferromagnets is extremely limited. In fact, it includes only the 2,2,5,5-and 4,4,5,5-tetramethyl derivatives of 3and 2-imidazoline, respectively.2,3 According to current concepts, nitroxides with one of the carbon atoms being a to the nitroxyl group and carrying an H atom are kinetically unstable and disproportionate to diamagnetic compounds.4Recently, terf-butyl diphenylmethyl nitroxide, L, has been reported as a representative of a new family of such a-Hcontaining nitroxides which are stable in the solid state as well as in solution.5 In these spin carriers the extensive functionalization of the carbon framework is possible and since the '-O group is less sterically hindered than that in fully -substituted analogs, the use of such spin carriers as building blocks in the design of exchange-coupled species is antici-* Author to whom correspondence should be addressed.(1) (a) International Tomography Center, (b) Centre d'Etudes Nucleates,

Crystal structures and magnetic properties of mercury(II) bromide complexes with pyridyl-substituted N-oxyl N′-oxides (nitronyl nitroxides)

“…where x = J/2kT, N = 1.0 ϩ 5.797 991 6x ϩ 16.902 653x 2 ϩ 29.376 885x 3 ϩ 29.832 959x 4 ϩ 14.036 918x 5 and D = 1.0 ϩ 2.797 991 6x ϩ 7.008 678 0x 2 ϩ 8.653 864 4x 3 ϩ 4.574 311 4x 4 . The solid curve in Fig.…”

“…The magnetic properties of a large number of stable organic Noxyl NЈ-oxides (nitronyl nitroxides) and their metal complexes have been studied, especially in order to understand the factors that influence the magnetic exchange interactions between the metal ion and the radical centers. [1][2][3][4] Recently, several magnetic properties of pyridyl-substituted N-oxyl NЈ-oxide radicals [5][6][7][8] and their metal complexes 9-15 have been reported. These radicals are especially attractive due to their donor atoms and to assemble an extended co-ordination geometry with changing magnetic coupling.…”

Structure and magnetic properties of copper(II) carboxylate with pyridyl-substituted nitronyl nitroxides

“…The magnetic properties of a large number of stable organic N-oxyl N%-oxides (nitronyl nitroxides) and their metal complexes have been studied, especially in order to understand the factors that influence the magnetic exchange interactions between the metal ion and the radical centers [1][2][3][4][5][6][7][8]. The magnetic metal complexes with pyridyl-substituted nitronyl nitroxides have been intensively studied [1,2,4 -19] in the past decade.…”