ESR Study of thet-Pentyl Derivative of Yang’s Biradical

An asymmetrical t-pentyl derivative of Yang’s biradical was prepared, and the g- and D-tensor values of the biradical were determined from an analysis of an asymmetric ESR spectrum of a frozen solution containing the biradical. The result may be understood by assuming that the benzene ring onto which two pentyl groups are substituted is twisted more than the other two benzene rings. On the other hand, the fluid solution ESR spectrum shows seven hyperfine splittings due to six equivalent meta ring protons in the three benzene rings of the pentyl derivative.