Fig. 2: X-ray solid-state structures of the TPA–NHC precursors and their corresponding carbon-centered radicals.

a X-ray solid-state structures for precursor 1a^I and radical 3a^I. b X-ray solid-state structures for precursor 1b^I and radical 3b^I. c X-ray solid-state structures for precursor 1c^I and radical 3c^I. d X-ray solid-state structures for precursor 1b^III and radical 3b^III. θ: the twisted angle between the C3–C2–C4 and N1–C1–N2 plane. The single crystals of radical precursors 1a^I, 1b^I, 1c^I, and 1b^III were grown by slowly diffusing diethyl ether into a saturated acetonitrile solution at ambient temperature. The single crystals of radicals 3a^I, 3b^I, 3c^I, and 3b^III were obtained from a saturated hexane solution upon cooling to −30 °C. Thermal ellipsoids are shown with 50% probability. Color scheme: C, gray; N, blue; F, green. Hydrogen atoms, the counter anion, and solvent molecules are omitted for clarity. Selected bond lengths and angles Å and deg: (1a^I): C1–N1 1.348(3); C1–N2 1.351(3); <N1–C1–N2 106.47(17). (1b^I): C1–N1 1.349(3); C1–N2 1.353(3); <N1–C1–N2 106.65(19). (1c^I): C1–N1 1.334(2); C1–N2 1.337(2); <N1–C1–N2 110.84(13). (1b^III): C1–N1 1.343(4); C1–N2 1.345(4); <N1–C1–N2 106.9(3). (3a^I): C1–N1 1.399(2); C1–N2 1.403(2); <N1–C1–N2 103.81(14). (3b^I): C1–N1 1.398(2); C1–N2 1.402(2); <N1–C1–N2 105.04(14). (3c^I): C1–N1 1.397(4); C1–N2 1.400(4); <N1–C1–N2 108.5(3). (3b^III): C1–N1 1.4019(19); C1–N2 1.3974(18); <N1–C1–N2 104.33(12).