GENERATION OF TRICYANOMETHYL SPIN ADDUCTS OF ALPHA-PHENYL-N-TERT-BUTYLNITRONE (PBN) VIA NONCONVENTIONAL MECHANISMS

Spin adducts, formally derived from tricyanomethyl radical attachment to alpha-phenyl-N-tert-butylnitrone (PBN; IUPAC name: N-benzylidene-te rt-butylamine N-oxide), have been generated by various methods, such a s oxidation of a mixture of tricyanomethanide ion and PBN by tris(4-br omophenyl)aminium ion or bromine, photo-oxidation of a mixture of tric yanomethane and PBN with 2,4,6-tris(4-methoxyphenyl)pyrylium ion as a sensitizer, or photolysis of chlorotricyanomethane and PBN at -30 degr ees C, the low temperature being necessary to avoid fast concurrent cy cloaddition with PBN. Both the C- and N-connected spin adducts, (NC)(3 )C-PBN. and (NC)(2)C=C=N-PBN. have been characterized, as has an amino xyl formed by elimination of hydrogen cyanide from the former species, (NC)(2)C=C(Ph)N(O-.)Bu-t. For comparison, similar experiments have be en performed using carbamoyldicyanomethanide ion and carbamoylchlorodi cyanomethane and the spin adduct H2NCO(CN)(2)C-PBN. has been character ized, The redox properties of tricyanomethanide ion, carbamoyldicyanom ethanide ion, chlorotricyanomethane and carbamoylchlorodicyanomethane have been studied by cyclic voltammetry. For chlorotricyanomethane, th e redox reactivity has also been evaluated by its propensity to genera te radical cations from aromatic substrates ArH in 1,1,1,3,3,3-hexaflu oropropan-2-ol. Tricyanomethanide ion has E[(CN)(3)C-./(CN)(3)C-](rev) at 1.35 V (vs, Ag/AgCl) in acetonitrile while chlorotricyanomethane w ith E-pc about 0.6 V and a capability to oxidize compounds with redox potentials up to ca, 1.5 V to radical cations, emerges as belonging to the strongest neutral organic electron accepters.