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.
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