A study of π-conjugation in Chichibabin's - and Schlenk's - like hydrocarbons with ESR : Part I

Analysis of the ESR spectrum of the radical cation, derived from p, p'-bis-{phenyl(triphenylphosphorylidene)methyl}biphenyl reveals that spin density is found at both 31P nuclei. Zero spin density is indicated for the outer phenyl rings. In the radical cation, derived from the corresponding m,m'-isomer the spin density is delocalized over one half of the molecule and interaction is found with only one phosphorus atom. In this system the spin density in the outside ring exceeds that in the biphenyl ring. The localization of the odd electron on one half of the molecule must be caused by a strong Jahn-Teller effect. The assignment of the hyperfine coupling constants was based on spin density calculations according to the Unrestricted Hartree-Fock (UHF) method. From these calculations we also obtained an indication of the geometry of the radicals. The synthesis of these compounds is reported