Radical cations from N-alkyl substituted imines: an EPR study

Abstract

Following γ-radiolysis of dilute solutions of imines in trichlorofluoromethane at 77 K, EPR spectra of the corresponding radical cations were recorded. For PhCHNEt and PhCHNCHMe2 the primary 2A′ cations were formed, but in each case as a mixture of cations with different conformations of the alkyl group. The complex spectra were assigned with the aid of those for the deuteriated analogues PhCDNEt and PhCDNCHMe2. For Ph2CNEt, two cations differing by the confomation of the ethyl group were observed; for Ph2CNCHMe2, only a single conformer was evident. In an attempt to induce a σ/π‘crossover’, the compounds p-Cl–C6H4CHNBut and p-MeO–C6H4CHNBut were studied: the latter did indeed form a π-cation, while the former gave the normal 2A′ cation. The neopentyl derivatives PhCHNCH2But and Ph2CNCH2But gave only the distonic radical cations PhCH[graphic omitted]H–CH2C(Me2)CH2˙ and Ph2C[graphic omitted]H–CH2C(Me2)CH2˙, formed by an intramolecular hydrogen atom transfer. By studying the series of deuteriated compounds, PhCDNCH2CH2CH2CH3, PhCDNCD2CH2CH2CH3 and PhCHNCD2CH2CH2CH3, it is shown that, on radiolytically-induced single electron oxidation, PhCHNBu gives the distonic radical cation PhCH[graphic omitted]HCH2CH2ĊHCH3.