Spectroscopic studies of various carbene–radical-cations fromed by radiolysis of solutions on halogenocarbons

Abstract

Cationic species produced in the γ-radiolysis of the halogenocarbon–aryldiazomethane mixtures have been studied at 77 K by electron spin resonance (e.s.r.) and optical absorption spectroscopy. A diphenyldiazomethane radical-cation ([(C₆H₅)₂CN₂]⁺˙) produced by the radiolysis of n-C₄H₉Cl–(C₆H₅)₂CN₂(0.1 mol %) mixtures is found to have an absorption band at 650 nm. When the cation is irradiated with visible light, a different cation is produced which has an absorption spectrum at 390 nm, interpretable in terms of a diphenyl carbene radical-cation ([(C₆H₅)₂C]⁺˙). A phenyldiazomethane radical cation ([C₆H₅CHN₂]⁺˙) and a phenylcarbene radical-cation ([C₆H₅CH]⁺˙) have absorption bands at 515 and 475 nm, respectively. The e.s.r. spectrum of [(C₆H₅)₂CN₂]⁺˙ cations, produced by the radiolysis of CCl₃F–(C₆H₅)₂CN₂(0.2 mol %) mixtures at 77 K, shows a broad singlet spectrum. Upon irradiation with visible light the broad spectrum changes into a sharp singlet, which is ascribed to [(C₆H₅)₂C]⁺˙ cations. Formation of [C₆H₅CHN₂]⁺˙ and [C₆H₅CH]⁺˙ cations has also been studied by e.s.r. spectroscopy. The effect of deuteriation on the e.s.r. spectra has been stuided by use of deuteriated aryldiazomethanes, such as (C₆D₅)₂CN_2′ C₆H₅CDN_2′ and C₆D₅CDN₂.