Negative ions, molecular electron affinity and orbital structure of cata‐condensed polycyclic aromatic hydrocarbons

Abstract

The obtained results contribute to the field of electron-molecule interactions and may be of importance for the better comprehension of the functioning of organic electronics, for the synthesis of relevant novel materials, and the development of efficient analytical methods capable of discriminating structural isomers.

Comment on: Negative ions, molecular electron affinity and orbital structure of cata‐condensed polycyclic aromatic hydrocarbons by Rustem V. Khatymov, Mars V. Muftakhov and Pavel V. Shchukin

“…One of the major criticisms of the ECD method is that the products of the reaction are not identified. However, the lifetimes reported in both studies by Khatymov et al support the assumption that the products in the ECD are the molecular negative ions of these molecules. In addition, the recent determination of the electron affinity of phenanthrene by photon studies demonstrates that its electron affinity is positive .…”

“…Table shows the ground state AE a for the AHC considered herein, the ionization energies from the NIST database and the lifetimes from the subject article and Khatymov et al There are reported photon AE a values for anthracene, 0.530 (8) eV; pyrene, 0.41 (1) eV; and chrysene, 0.32 (1) eV, in the NIST database . Not in the database, however, is the photon AE a value for phenanthrene of 0.12 eV .…”

“…"For the PAH molecules one can find numerous literature data on experimental electron affinities, which are often poorly consistent with each other […] In view of lack of reliable data, the adiabatic EA for PAH molecules can be assessed using simple regularity EA + IE ≈ 8 eV (consequence of nearly equal electronegativity of PAH molecules) where IE is the vertical ionization energy of the molecule. " Table contains the evaluated ionization energies in the NIST database which, when combined with the ground state AE a , give a constant eletronegativity.…”

“…Aromatic hydrocarbons with gs‐AE a from 0.4 to 0.7 eV form anions of the molecule with lifetimes of the order of 40–50 μs at thermal energies although the exact values cannot be compared because of the temperature dependence of the lifetimes. The lifetime of 9‐phenylanthracene with a predicted AE a of 0.69 eV was reported to be 145 μs . Based on this value, the lifetime of benz(a)pyrene with a ground state AE a of 0.82 (2) eV will be greater than 150 μs.…”

“…The electron affinities of polycyclic aromatic hydrocarbons (PAHs) are important properties with reported experimental values that differ by more than the uncertainties, as observed in the subject article . These differences occur because the values have not been assigned to ground and excited states.…”