Nitroxides. XIV. A Stable Biradical in the Nitroxide Series

Abstract

leads to the conclusion that HeF2 is highly unlikely to be bound. This prediction based on this qualitative argument has been stated several times in recent theoretical treatments,6-8 yet, not unexpectedly, this simple argument is stated with considerably less conviction than would be expressed by a chemist who had no knowledge of xenon chemistry. In fact, a detailed and well-reasoned communication has been published claiming the likely existence of a stable HeF2.9 It is for these reasons that the qualitative chemical arguments and their manifestation in terms of simple Hiickel-like model theories6-8•10 are subject to the "strong inference" criticism of Platt11 and are inadequate to answer decisively the question of the existence of HeF2. It is also necessary that the electronic wave function for the HeF2 system be complete enough to provide a description of the free helium atom at the same level of accuracy as that needed to produce a smooth change from a free xenon atom at infinite separation to the observed stable binding. This has been accomplished in our wave function by carrying the ionic state and in-out configuration interaction into the free helium atom as infinite separation is approached.

Structure cristallographique du biradical tétraméthyl-2,2,5,5 aza-1 cyclopentanone-3 azine-3 oxyle

“…(Dupeyre, Lemaire & Rassat, 1965). Ces radicaux pr6sentent un grand int6r& du fait de leur stabilit6 et font l'objet de nombreuses ~tudes: propri6t6s chimiques, susceptibilit6 magn6tique, chaleur sp6-cifique, r6sonance paramagn6tique 61ectronique (r.p.e.)…”

Hyperfine structure of ESR spectra as a probe for heisenberg exchange couplings in nitroxide triradicals serving as building blocks for molecule-based ferrimagnets

“…Our focus in this paper is on organic oligoradicals in which two or more unpaired electrons are exchange-coupled within a single molecule. The analysis of the hyperfine structure of the ESR spectra of exchange-coupled systems dates back to pioneering works of Weissman [3], Luckhurst [4] and Rassat [5,6]. The hyperfine structure of ESR spectra in solution is revived in terms of molecular magnets.…”

Affinement de la structure du radical nitroxyde dimerisé: bicyclo[3,3,l]nonanone-3 aza-9 oxyle-9

“…1) est un des radicaux libres nitroxydes synthdtisds et dtudids au Laboratoire de Chimie Organique Physique du C.E.N.G. (Dupeyre & Rassat, 1966). Ces radicaux sont les marqueurs de spins les plus employds (Hamilton & McConnell, 1968).…”