Electron Spin Dynamics of Photoexcited Corannulene-Lithium Complexes in Tetrahydrofuran. Fourier Transform Electron Paramagnetic Resonance

Tuning the separation and coupling of corannulene trianion-radicals through sizable alkali metal belts

“…Previously, paramagnetic C 20 H 10 ˙ 3– radicals were detected in situ by ESR spectroscopy using a reduction reaction of corannulene with lithium metal in THF. 24 We have observed that Li-induced reduction of corannulene quickly proceeds to the final reduction state, C 20 H 10 4– , and thus is impractical for the preparation of products based on transient trianions. However, the outcome of using other Group 1 metals in these reactions remained unclear.…”

Supramolecular trap for a transient corannulene trianion

“…Previously, the paramagnetic C 20 H 10 ˙ 3– radical was detected by ESR spectroscopy using the in situ reduction reaction of corannulene with lithium metal in THF. 24 The ESR data provided the only evidence of existence of this transient species in solution, as the initially reported UV-vis spectroscopic data for the C 20 H 10 ˙ 3– anion 24 a have been later re-assigned to the tetrareduced state of corannulene. 25 The question whether the corannulene trianion engages in self-assembly with alkali metal ions or can exist in discrete form has remained open.…”

π-Conjugated Anions: From Carbon-Rich Anions to Charged Carbon Allotropes

“…The EPR spectrum of the corannulene mono-radical anion 5 •-shows an 11-line hyperfine pattern (αH ϭ 0.157 mT) for the ten equivalent protons. [35,36] Differences seen with potassium and lithium as counterions are negligibly small. [30] Counterion couplings were observed in the triradical anion lithium species.…”

“…[30] Counterion couplings were observed in the triradical anion lithium species. [36] The trianion radical of 5 with lithium (5 •3-) shows a highly resolved EPR spectrum where additional 7 Li (and 6 Li [36] ) couplings are evident [g ϭ 2.0025, αH ϭ 1.62 mT, α 7 Li (I ϭ 3/2) ϭ 0.04-0.10 mT]. [30] As no change in the characteristic hyperfine pattern could be observed in the EPR spectra of the trianion radical over the entire reduction process from the di-to the tetraanion, a dimerization process for the trianion can be ruled out.…”