The radical anion of tetraphenylene revisited

Abstract

The tetraphenylene radical anion (2˙^–) generated by Na, K and Cs reduction in tetrahydrofuran and 2-methyltetrahydrofuran has been investigated by EPR/ENDOR spectroscopy. The results clearly establish that the decrease of the molecular symmetry of 2˙^– from D_2d to C_2v detected upon exhaustive reduction arises from ion-pair formation. This finding unequivocally rules out the assumption stated in previous papers that the EPR spectra mirroring the lower symmetry originate in a bis(biphenylene)-like geometry of 2˙^–.