Electron Resonance Studies of Perchlorodiphenylmethyl and Perchlorotriphenylmethyl Free Radicals

The stable free radicals perchlorodiphenylmethyl, (C₆Cl₅)₂ĊCl, and perchlorotriphenylmethyl, (C₆Cl₅)₃C, have been examined by electron resonance. In solution, the isotropic α‐chlorine hyperfine splitting in PDM was found to be 6.08 Mc/sec. Splittings from ¹³C in natural abundance at the methyl carbon (about 100 Mc/sec) and at additional phenyl–carbon sites were measured for both radicals. By incorporating PDM in the liquid crystal p‐azoxyanisole, the principal values of the anisotropic hyperfine coupling tensor of the $\alpha$ chlorine were derived and found to be $A_{11}\text{\hspace{0.17em}=\hspace{0.17em}−\hspace{0.17em}9.2}$ , $A_{22}\text{\hspace{0.17em}=\hspace{0.17em}−\hspace{0.17em}18.9}$ , and $A_{33}\text{\hspace{0.17em}=\hspace{0.17em}47.2}\mathrm{Mc}/\sec$ . The variation with temperature of the degree of ordering of the radicals in the nematic mesophase was determined.