Detection par R.P.E. de changements de conformation induits par le solvant.

Controlling the Extent of Spin Exchange Coupling in 2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO) Biradicals via Molecular Recognition with Cucurbit[n]uril Hosts

“…The observed spectra may oscillate between two extremes: (1) a simple three-line spectrum (1:1:1 intensities) that reflects the complete lack of exchange coupling between the two nitroxides and (2) a five-line spectrum (1:2:3:2:1 intensities) when the spin system is completely delocalized . Compound 2 is anticipated to exhibit an intermediate degree of spin exchange coupling, as the two TEMPO units can exist in multiple conformations, resulting from the relative rotation of the cyclopentadienyl rings around their main axis …”

Novel ferrocenyl nitroxides: Synthesis, structures, electrochemistry and antioxidative activity

“…Since the first member (t-butylferrocenylnitroxide) was reported at 1969 [1], the family of metallocenyl substituted nitroxide radical (McNO) became an important kind of compounds in the interdisciplinary field between organometallic and free radical field [2][3][4]. Most McNOs research had focused on discussing the intermolecular ferromagnetic interaction, and aimed at the preparation of high-spin materials [5,6], but other potential properties and application of McNOs have been extensively overlooked.…”

“…The present McNO molecular design and synthesis have been just confined to introducing different nitroxide moiety into different metallocenyl ring directly or by a short linkage [2,6,7]. However, using various longer conjunctional linkage bridging the metallocene and the nitroxide moieties, could be an even better choice with many alternatives, which has been less reported, presumably because of the ambiguity of the relationship between linkage structure and compounds properties.…”

“…So in the development of novel functional McNOs, two fundamental issues must be addressed, (1) whether the longer and more complex linkage improves the McNO properties? (2) and how does it improve these properties?…”