A Guide to Tris(4-Substituted)-triphenylmethyl Radicals

Abstract

Triphenylmethyl (trityl, Ph3C•) radicals have been considered the prototypical carbon-centered radical since their discovery in 1900. Tris­(4-substituted)-trityls [(4-R-Ph)3C•] have since been used in many ways due to their stability, persistence, and spectroscopic activity. Despite their widespread use, existing synthetic routes toward tris­(4-substituted)-trityl radicals are not reproducible and often lead to impure materials. We report here robust syntheses of six electronically varied (4-RPh)3C•, where R = NMe2, OCH3, t Bu, Ph, Cl, and CF3. The characterization reported for the radicals and related compounds includes five X-ray crystal structures, electrochemical potentials, and optical spectra. Each radical is best accessed using a stepwise approach from the trityl halide, (RPh)3CCl or (RPh)3CBr, by controllably removing the halide with subsequent 1e– reduction of the trityl cation, (RPh)3C+. These syntheses afford consistently crystalline trityl radicals of high purity for further studies.

Structure–property–function relationships of stabilized and persistent C- and N-based triaryl radicals

“…[5][6][7] More specifically, several efficient design approaches have been established to ensure the stabilization and persistence of C-and N-based triaryl radicals. 6,[8][9][10] But novel applications of the radicals demand further advances in design strategies to yield targeted physical, photophysical and electronic properties, chemical reactivity and response output.…”