The synthesis and characterization of 11 inert diradicals of the perchlorotriphenylmethyl class, (p)R-C-6-Cl-4(C6Cl5)C-C6Cl4-Sp-C6Cl4-C(C6Cl5)-C6Cl4-R(p) where R is Cl, OH, or O- and Sp is a spacer chain from zero to nine atom links, are described. The ESR spectra of these species in solution from room temperature to -140 degrees C (glassy matrix) point to the concurrence of two isomeric diradical forms : the conventional species, displaying spin-spin dipolar interaction, and a form apparently devoid of it. The ESR C-13 hyperfine couplings, the magnetic susceptibility, and the IR and UV-vis spectra of these diradicals are described. Some related monoradicals and a triradical are also reported.