C 20 Carbon Clusters: Fullerene–Boat–Sheet Generation, Mass Selection, Photoelectron Characterization

Electron‐impact ionization in a time‐of‐flight mass spectrometer of C 20 H 0–3 Br 14–12 probes—secured from C 20 H 20 dodecahedrane by a “brute‐force” bromination protocol—provided bromine‐free C 20 H 0–2(3) anions in amounts that allowed the clean mass‐separation of the hydrogen‐free C 20 − ions and the photoelectron (PE) spectroscopic characterization as C 20 fullerene (electron affinity (EA)=2.25±0.03 eV, vibrational progressions of 730±70). The extremely strained C 20 fullerene ions surfaced as kinetically rather stable entities (lifetime of at least the total flight time of 0.4 ms); they only very sluggishly expel a C 2 unit. The HOMO and LUMO are suggested to be almost degenerate (Δ E =0.27 eV). The assignment as a fullerene was corroborated by the PE characterization of the C 20 bowl (EA=2.17±0.03 eV, vibrational progression of 2060±50 cm −1 ) analogously generated from C 20 H 10 corannulene (C 20 H 1–3 Br 9–8 samples) and comparably stable. Highly resolved low‐temperature PE spectra of the known C 20 ring (EA=2.49±0.03 eV, vibrational progressions 2022±45 and 455±30 cm −1 ), obtained from graphite, display an admixture of, most probably, a bicyclic isomer (EA=3.40±0.03 eV, vibrational progression 455±30 cm −1 ). The C 20 +(−) and C 20 H 2 +(−) cluster ions generated from polybrominated perylene (C 20 H 0–2 Br 12–10 ) have (most probably) retained the planar perylene‐type skeleton (sheet, EA=2.47±0.03 eV, vibrational progressions of 2089±30 and 492±30 cm −1 and EA=2.18±0.03 eV, vibrational progressions of 2105±30 and 468±30 cm −1 ).