Detection of propane-cation radical with an asymmetric structure by electron spin resonance

The propane-cation radical of C s symmetry with one of the C—C bonds elongated, was detected by ESR in a frozen C 3 F 8 matrix at 4 K; this asymmetric structure has been predicted theoretically to be the most stable form. The singly occupied molecular orbital is 10a′ which spreads over the entire molecular plane, analogously to the 4b 1 orbital of the propane cation with C 2v symmetry in SF 6 . In the C s cation, however, the unpaired electron density in the elongated C—C σ-bond is much higher than that in the other part of the molecule. Above 77 K, interconversion between the two equivalent deformed structures makes the hfc's of the two inplane protons equal to each other. The averaged value is approximated one half that of the c 2v cation. The role of matrix molecules in the electronic structure and the dynamics of the propane-cation is discussed.