Electron affinity of modified benzene

Abstract

The electron affinities of organic molecules obeying H€ uckel's rule of aromaticity are vanishingly small, if not negative. For example, benzene, a classic example of an aromatic molecule, has an electron affinity of 21.15 eV. Using density functional theory, we have systematically calculated the electron affinities and vertical detachment energies of C 6 H 6 by substituting H with halogen (F) and superhalogen (BO 2 ) moieties, as well as replacing one of the C atoms with B. The ground state geometries were obtained by examining about 330 isomers. The electron affinities are found to steadily increase with these substitutions/replacements, even surpassing that of Cl, the element with the highest electron affinity in the periodic table, in the case of C 5 BH(BO 2 ) 5 . In some special cases such as C 6 H 5 (BO 2 ) the electron affinity and vertical detachment energy differ by as much as 5 eV, indicating substantial changes in the geometry as the electron is removed from the anion.We hope that the ability to change the negative electron affinity of C 6 H 6 to large positive values by substituting H and/or replacing C atom will motivate experimental studies.benzene, electron affinity, H€ uckel's rule, superhalogen 1 | I N TR ODU C TI ON Negative ions play an important role in chemistry as strong oxidizing agents. Among all elements in the periodic table, halogens readily form negative ions with F being the most electronegative element and Cl having the highest electron affinity, namely 3.6 eV, among elements in the periodic table. More than half a century ago, a new chapter in negative ion chemistry opened when Bartlett and coworkers [1,2] discovered that the O 2 molecule, as well as the Xe atom can be oxidized by PtF 6 . The authors estimated the electron affinity of PtF 6 to be in excess of 6.76 eV. In the early 1980s, Boldyrev and Gutsev [3][4][5][6] coined the word superhalogen to describe the properties of molecules like PtF 6 . They showed that a cluster containing a metal atom, M, of valence k at the core and decorated with (k 1 1) number of halogen, X, atoms would have electron affinities that are larger than that of the halogen atom they are composed of. Thus, MX (k11) would constitute a class of clusters that mimics the chemistry of halogen atoms. Because their electron affinities are larger than those of halogen atoms, superhalogens can also form chemical bonds with atoms having rather high ionization potentials. That XePtF 6 could form in spite of the large ionization potential of Xe, namely 12.2 eV, [7] bears testimony to the unusual chemistry of superhalogens. In addition to allowing noble gases to participate in new chemistry, [8] superhalogens have been recently found to lead to a new generation of electrolytes in Li ion batteries [9][10][11][12] and hybrid perovskite-based solar cells. [13,14] The utility of superhalogens in the design and synthesis of new materials of technological importance has spurred considerable interest not only in expanding their scope but also in finding ways to enhance the...

Mg3F7: A superhalogen with potential for new nanomaterials design

“…One of the principal factors which imply molecular reactivity in chemistry is electron affinity (EA) . Explicitly, species with high EA typically act as strong oxidizing agents in chemical processes and capture an excess electron to become strongly bound negative ions.…”

“…K E Y W O R D S magnesium fluorides, polynuclear anions, spin density distribution, theoretical nanoscience, vertical electron detachment energy 1 | INTRODUCTIONOne of the principal factors which imply molecular reactivity in chemistry is electron affinity (EA). [1,2] Explicitly, species with high EA typically act as strong oxidizing agents in chemical processes and capture an excess electron to become strongly bound negative ions. As it is well known, among the chemical elements halogen atoms exhibit the largest EAs (fluorine 3.40 eV, chlorine 3.62 eV).…”

Overview of antiproton affinities for functional groups relevant in particle‐beam cancer therapy

“…Similar work has been carried out regarding proton affinities for amino acids in Dinadayalane et al, Bleiholder et al, and Gronert et al, proton‐molecule collisional reaction mechanisms from studying PES in Wang et al, and electron affinities in Driver and Jena . For antiproton affinities, a related topic is the capture probability of muons, since a muon has the same charge and comparable mass (about 9 times smaller) to an antiproton.…”

Negative ion formation and fragmentation upon dissociative electron attachment to the nicotinamide molecule

“…This observation is in line with previous studies of electron capture by the pyridine and benzene derivatives, in which the parent anion was also not measured. [42][43][44][45] Nevertheless, the EA of the benzene as well as pyridine is negative, 46,47 whereas the EA of the NA molecule is positive, equal to 0.25- 48 Hence, it may be proposed that for NA, the formation of the stable parent anion is possible but due to the low efficiency of this process, the anion yield is below the detection limit of the apparatus. The electron attachment resonance positions were determined by tting Gaussian peaks to the experimental data, whereas the anion appearance energy (AE) was estimated using the procedure described by Meißner et al in ref.…”

“…This observation is in line with previous studies of electron capture by the pyridine and benzene derivatives, in which the parent anion was also not measured. 42–45 Nevertheless, the EA of the benzene as well as pyridine is negative, 46,47 whereas the EA of the NA molecule is positive, equal to 0.25–0.40 eV (see Table 1 ). The EA of NA is close to the EA of 0.45 eV for the other recently investigated molecule, (CH 3 S) 2 CS, for which the parent anion was observed.…”