C20 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 (DeltaE=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)).
Prinzbach
Horst
H
Institut für Organische Chemie und Biochemie, Albert-Ludwigs-Universität, 79104 Freiburg, Germany. horst.Prinzbach@orgmail.chemie.uni-freiburg.de
Wahl
Fabian
F
Weiler
Andreas
A
Landenberger
Peter
P
Wörth
Jürgen
J
Scott
Lawrence T
LT
Gelmont
Marc
M
Olevano
Daniela
D
Sommer
Frank
F
von Issendorff
Bernd
B
D000480:Alkynes / Q000737:chemistry; D037741:Fullerenes / Q000737:chemistry*; D006842:Hydrocarbons, Brominated / Q000737:chemistry; D013058:Mass Spectrometry; D008968:Molecular Conformation; D011083:Polycyclic Compounds / Q000737:chemistry*
D000480:Alkynes; D037741:Fullerenes; D006842:Hydrocarbons, Brominated; D011083:Polycyclic Compounds; C062580:dodecahedrane