Facile Generation of A₂B Corrole Radical Using Fe(III) Salts and Its Spectroscopic Properties

A carboxyphenyl-substituted corrole, 5,15-dimesityl-10-(4'-carboxyphenyl)corrole (1), has been synthesized and characterized by UV-vis, fluorescence, ¹H NMR spectroscopy, and electrospray ionization (ESI)-mass spectrometry (MS) techniques. An air-stable corrole radical (1^•) was obtained with the addition of the Fe(III) salt to 1 in dimethyl sulfoxide (DMSO) and characterized by UV-vis, fluorescence, electron paramagnetic resonance (EPR), ESI-MS techniques, and density functional theory studies. The neutral corrole radical (1^•) exhibited a sharp EPR signal at g = 2.006 in DMSO. The reduced bipyrrolic (N-C-C-N) dihedral angle (χ) of 1 from 19.11 to 7.07° leads to the release of angle strain, which is the driving force for the generation of 1^•. Notably, trans-dimesityl groups prevent the dimerization or aggregation of the corrole radical. Further, 1^• was converted to 1 by excess addition of Fe(II) salts in DMSO at 298 K.