Spin Density Distribution in 2,4,6-Triphenylphenoxyl

The distribution of the unpaired electron over the oxygen and the 24 carbon atoms in the free 2,4,6-triphenylphenoxy radical was determined by electron spin resonance spectroscopy and quantum-mechanical approximation methods. The hyperfine splitting was evaluated with the aid of the spectra of triphenylphenoxyls deuterated in some or all of the substituent phenyl groups. The results of the quantum-mechanical approximations were checked by recording the ESR spectra of triphenylphenoxyls labeled with ¹³C in positions 1,2,3, or 4 of the central ring. The spin density distribution permits a first discussion of the ¹⁷O-coupling constants of correspondingly labeled triphenylphenoxyl and other organic free radicals.