Bottleable “Ph3C·”: Negligible Electronic Perturbation by Peripheral Steric Protection

We report the isolation and characterization of six triarylmethyl radicals ((3,5-Mes2C6H3)3C· (29), (4-MeO-3,5-Mes2C6H2)3C· (30), (4-F-3,5-Mes2C6H2)3C· (31), (4-Cl-3,5-Mes2C6H2)3C· (32), (4-Br-3,5-Mes2C6H2)3C· (33), (4-I-3,5-Mes2C6H2)3C· (34) stabilized by bulky mesityl substituents in the meta-positions. The radicals were characterized by EPR and UV-vis spectroscopy (29–34), and single-crystal X-ray diffraction (sc-XRD) (29). The energies of their frontier orbitals with and without mesityl groups are compared by density functional theory (DFT) calculations. The negligible electronic perturbation makes 29 an excellent model for the parent trityl radical Ph3C·.