Nitroxide. 84. Copper(II)-bisnitroxide complex as evidence for strong electron-exchange six-spin system

Yttrium(III) and lanthanide(III) perchlorate complexes with the 2,2,6,6- tetramethylpiperidine nitroxide free radical

“…Ethanol-acetone (1 : 1, v:v) solution e.s.r, spectra of the new paramagnetic Ln 3+ ion complexes (Ln = Ce -Yb) are generally similar to those of solutions of uncomplexed TMPNO, exhibiting three equally spaced, equally intense lines, which are characteristic of a single unpaired electron interacting with a single nitrogen nucleus (62' 6:3). Such e.s.r, spectra are not unusual for solutions of complexes of nitroxide radicals with paramagnetic metal ions (v' IO); it should be noted, however, that, quite recently, e.s.r, spectra exhibiting hypcrfinc structure have bcen recorded for heptanc solutions of Cu H nitroxide radical complexes, involving strong electron exhange (64). For ethanol-acetone solutions of the ncw Y 3÷ and La 3÷ complexes, multi-line e.s.r, spectra were obtained; no satisfactory resolution has been achicvcd so far for these spectra, and experiments in this dircction are to be continued.…”

Copper(II)-Nitroxide Based Spin-Transition Like Species

“…Much of the popularity of copper(II) in these systems sterns from the simplicity of the magnetic features of this non-orbitally degenerate metal ion possessing a single unpaired electron. Syntheses of copper(II)-nitroxide species were first devoted to EPR studies in solution [1][2][3][4][5]and soon after to the investigation oftheir magnetic properties in the solid state. Since the nitroxyl group is a poor Lewis base, most of the complexes involve acidic metal centers such as hexafluoroacetylacetonates.…”