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

Triphenylmethyl (trityl, Ph3C & BULL;) radicalshavebeen considered the prototypical carbon-centered radical since theirdiscovery in 1900. Tris(4-substituted)-trityls [(4-R-Ph)(3)C & BULL;] have since been used in many ways due to their stability,persistence, and spectroscopic activity. Despite their widespreaduse, existing synthetic routes toward tris(4-substituted)-trityl radicalsare not reproducible and often lead to impure materials. We reporthere robust syntheses of six electronically varied (4-RPh)(3)C & BULL;, where R = NMe2, OCH3, Bu- t , Ph, Cl, and CF3. The characterizationreported for the radicals and related compounds includes five X-raycrystal structures, electrochemical potentials, and optical spectra.Each radical is best accessed using a stepwise approach from the tritylhalide, (RPh)(3)CCl or (RPh)(3)CBr, by controllablyremoving the halide with subsequent 1e(-) reductionof the trityl cation, (RPh)(3)C+. These synthesesafford consistently crystalline trityl radicals of high purity forfurther studies.

Automated summary

Triphenylmethyl (trityl) radicals have been widely used since their discovery in 1900 due to their stability, persistence, and spectroscopic activity. However, existing synthetic routes to tris(4-substituted)-trityl radicals often result in impure materials. In this study, we report robust syntheses of six electronically varied trityl radicals, providing high purity crystalline materials for further research.