392-56-3Relevant articles and documents
Temperature-enhanced electron detachment from C6F6- negative ions
Datskos, P. G.,Christophorou, L. G.,Carter, J. G.
, p. 7875 - 7882 (1993)
A method is described whereby photoelectrons generated by a short laser pulse at the cathode of a parallel-plate electrode arrangement are depleted by attachment to C6F6 molecules mixed with N2 in the interelectrode space as they drift to the anode under an externally applied electric field.The contribution of the initially produced (prompt) and the delayed (autodetached from C6F6-) electrons to the induced signal in the detector circuit is recorded as a function of time following the laser pulse and also as a function of gas number density, applied electric field, and gas temperature, T.Increases in T from ambient to 575 K enhance dramatically the autodetachment frequency, τd-1, for C6F6-.This heat-activated autodetachment correlates with the increase in the internal energy of the anion and has an activation energy of 0.477 eV.Electron attachment producing C6F6- initially increases slightly with increasing T below 500 K and subsequently decreases with further increases in T.
Perfluorobarrelene
Ralli, Philip,Zhang, Yin,Lemal, David M.
, p. 7349 - 7351 (2008)
The title fluorocarbon has been synthesized in three steps from cis-5,6-dichlorohexafluorocyclohexa-1,3-diene, a hexafluorobenzene synthon. Photolysis of perfluorobarrelene yields perfluorocyclooctatetraene. An extremely facile retro-Diels-Alder reaction is also described.
Laser Photodetachment Spectra of C6F6- in Nonpolar Liquids
Sowada, Ulrich,Holroyd, Richard A.
, p. 1150 - 1154 (1980)
Aromatic anions absorb in the visible region of the spectrum and energetic considerations suggest that in solution photodetachment may be an important process at these wavelengths.This study reports electron photodetachment cross sections for C6F6- for wavelengths between 415 and 700 nm.The anion is generated by electron attachment to solute C6F6 during an X-ray pulse.Detachment is observed as a change in conductivity induced by a subsequent light pulse from a tunable dye laser.The threshold values are reported for tetramethylsilane, n-butane, cyclopentane, n-pentane, 2,2,4-trimethylpentane, 2,2-dimethylbutane, and neopentane.The thresholds are consistent with an electron affinity of 1.09 +/- 0.04 eV for the C6F6 molecule.Comparison of the data to the absorption spectrum of C6F6- shows that for proton energies above threshold the major process is photodetachment.The relationship of photodetachment data to other properties of the excess electrons in these solvents is discussed.
Progress toward an absolute gas-phase proton affinity scale
Szulejko,McMahon
, p. 7839 - 7848 (1993)
The temperature dependence of the proton transfer equilibrium constants for approximately 80 pairs of bases ranging in proton affinity from N2 to tert-butylamine has been examined. These data provide the basis for formulation of a revised gas-phase proton affinity scale which now appears to have a firm basis. Excellent agreement with appearance energy determinations of proton affinities as well as ab initio calculated values is obtained. An important finding of this work is that the value of ΔHfo for the tert-butyl cation must be significantly higher than that derived from appearance energy measurements by Traeger which had formed the basis for the proton affinity assignment for isobutene, an important reference point in the proton affinity scale. The data obtained here would suggest that the proton affinity of isobutene must be revised downward by Δ4 kcal mol-1 with important consequence for all proton affinities in the vicinity of isobutene and above. In addition significant revisions are indicated for proton affinities between those of propene and isobutene. In contrast, however, the substantial upward revision of the proton affinity scale in the basicity region above ammonia which had been proposed by Mautner and Sieck (J. Am. Chem. Soc. 1991, 113, 4448) is not supported by the present experiments.
Ionizing reaction cross sections in the collision of argon atoms in high Rydberg states with various molecules
Dimicoli, I.,Botter, R.
, p. 2346 - 2354 (1981)
Measurements of absolute ionizing reaction cross sections in collisions between argon atoms in high Rydberg states (HR) and CCl4, CCl3F, CH3I, CF6, C6F6, CF4, and CO are reported together with their dependence on the HR argon velocity (570-2100 m/sec).The identity of the positively and negatively charged reaction products has been investigated with a coincidence TOF mass spectrometer.A comparison of the present data with results of other bound and free electron experiments and theoretical predictions is given.
Ion-pair formation in the collision of high Rydberg argon atoms with SF6 and C6F6 and negative ion lifetimes
Dimicoli, I.,Botter, R.
, p. 2355 - 2360 (1981)
The ion-pair formation in collision between argon atoms in high Rydberg states (HR) with SF6 and C6F6 has been investigated.The absolute cross sections are inversely proportional to the Ar(HR) velocity and increase monotonically with increasing principal quantum number n.Measurements of the negative ion lifetimes against autodetachment are reported and are above 20μsec for SF6- and ca 1μsec and above 20 μsec for C6F6-.The present data are reviewed in light of the theoretical predictions of "free electron" models and the results of free electron experiments.
Magnetic field effects on recombination fluorescence in liquid iso-octane
Saik, Vladimir O.,Ostafin, Agnes E.,Lipsky, Sanford
, p. 7347 - 7358 (1995)
The 123.6 nm photoionization of deuterated isooctane at -10 deg C in the presence of hexafluorobenzene has been studied by examining the effect of a magnetic field to alter the quantum yield of recombination fluorescence.This fiuorescence results from geminate recombination of hexafiuorobenzene anions with isooctane positive ions.The use of a deuterated as contrasted to a protonated alkane makes the intensity of the recombination fluorescence much more sensitive to the magnetic field and permits observation of two maxima in the fiuorescence yield at field strengths of 0 and 411 G and a possible third maximum at 822 G.The theory of the hyperfine induced spin evolution predicts these resonances at selected multiples of the C6F6- hyperfine constant of 137 G.Utilizing the diffusion theory of geminate recombination in a Coulomb field, the experimental magnetic field spectrum is found to be well predicted over most of the range of magnetic field strengths studied (up to 2.5 kG) by a simple, one parameter, exponential radial probability density of initial scavenged geminate pair separation distances.
Single and double ionization of corannulene and coronene
Schroeder, Detlef,Loos, Jessica,Schwarz, Helmut,Thissen, Roland,Preda, Dorin V.,Scott, Lawrence T.,Caraiman, Doina,Frach, Maxim V.,Boehme, Dielhard K.
, p. 1625 - 1634 (2001)
Electron-transfer processes that involve single and doubly charged cations of corannulene (C20H10) and coronene (C24H12) are examined by three different mass-spectrometric techniques. Photoionization studies give first-ionization energies of IE(C20H10) = 7.83 ± 0.02 eV and IE(C24H12) = 7.21 ± 0.02 eV. Photoionizations of the neutrals to the doubly charged cations occur at thresholds of 20.1 ± 0.2 eV and 18.5 ± 0.2 eV for corannulene and coronene, respectively. Energy-resolved charge-stripping mass spectrometry yields kinetic energy deficits of Qmin(C20H+10 = 13.8 ± 0.3 eV and Qmin(C24H+12 = 12.8 ± 0.3 eV for the transitions from the mono- to the corresponding dications in keV collisions. Reactivity studies of the C20H2+10 and C24H2+12 dications in a selected-ion flow-tube mass spectrometer are used to determine the onsets for the occurrence of single-electron transfer from several neutral reagents to the dications, affording two different monocationic products. With decreasing IEs of the neutral reagents, electron transfer to doubly charged corannulene is first observed with hexafluorobenzene (IE = 9.91 eV), while neutrals with lower IEs are required in the case of the coronene dication, e.g., NO2 (IE = 9.75 eV). Density-functional theory is used to support the interpretation of the experimental data. The best estimates of the ionization energies evaluated are IE(C20H10) = 7.83 ± 0.02 eV and IE(C24H12) = 7.21 ± 0.02 eV for the neutral molecules, and IE(C20H+10) = 12.3 ± 0.2 eV and IE(C24H+12) = 11.3 ± 0.2 eV for the monocations.
ELECTROPOLYMERISATION OF PERFLUOROCYCLO-ALKENES.
Briscoe, Mark W.,Chambers, Richard D.,Silvester, Michael J.
, p. 1295 - 1298 (1988)
Novel conducting materials are obtained by cathodic electropolymerisation of perfluoro-cyclobutene and -cyclopentene.
Laser-Induced Fluorescence Studies of Large and Small Molecular Cations Produced by Using Electron Bombardment in a Free Jet Expansion
Lester, Marsha Isack,Zegarski, B. R.,Miller, Terry A.
, p. 5228 - 5233 (1983)
Laser-induced fluorescence (LIF) excitation spectra have been obtained for a number of ions produced by electron impact in a free jet expansion.The ions observed include N2+, CO2+, C6F6+, C6F5H+, C6F3H3+, and C4H2+.In all cases "cold" laser excitation spectra have been obtained.For the simpler ions information about rotational distributions is available, while for the large ions the elimination of hot bands, sequence congestion, extensive rotational contours, etc., makes their spectra much easier to interpret.Under certain circumstances Penning ionization in the expansion effectively competes with direct ionization via electron impact.Some satellite structure is obtained in the C6F6+ spectrum which may be ascribed to C6F6+.Ar.
