Amino acids form strongly bound anions when substituted with superhalogen ligands

Sieradzan, Iwona; Anusiewicz, Iwona

doi:10.1063/1.4798320

Cited by 7 publications

(13 citation statements)

References 33 publications

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“…Until recently, much of the research on super‐ and hyper‐halogens focused on inorganic constituents. This is because the electron affinities of organic molecules are rather small.…”

Section: Introductionmentioning

confidence: 99%

Electron affinity of modified benzene

Driver

Jena

2017

Int J of Quantum Chemistry

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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...

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“…Until recently, much of the research on super‐ and hyper‐halogens focused on inorganic constituents. This is because the electron affinities of organic molecules are rather small.…”

Section: Introductionmentioning

confidence: 99%

Electron affinity of modified benzene

Driver

Jena

2017

Int J of Quantum Chemistry

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“…Furthermore, in some cases, such superhalogen substituents were found to render the anionic states stable (in a sense that a compound which does not form electronically stable anionic states was demonstrated to become capable of excess electron binding when the superhalogen substituent was introduced). This idea was successfully verified on certain well-known molecules (i.e., aliphatic and aromatic hydrocarbons [25], natural amino acids [26]) that do not bind extra electron. The resulting anions turned out to be very stable with their electron binding energies in the 4-6 eV range.…”

Section: Introductionmentioning

confidence: 96%

The PF₆₋_n(R)_n⁻anions (R = CH₃, C₂H₅;n= 0–6): the dependence of the electronic stability on the number of non-electronegative alkyl ligands

2014

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C 2 H 5 ; n = 0-6): the dependence of the electronic stability on the number of non-electronegative alkyl ligands, The PF 6−n (R) n − superhalogen anions (where R = CH 3 , C 2 H 5 and n = 1-6) were investigated at the ab initio OVGF/6-311 ++ G(3df,3pd)//MP2/6-311 ++ G(d,p) level of theory and their electronic and thermodynamic stabilities were compared to those of the reference PF 6− system. It is demonstrated that (1) the presence of six substituents bound to the phosphorus atom is an important factor that enables the stability of the PF 6−n (R) n − anions;(2) subsequent replacement of the fluorine ligands with alkyl R groups in the PF 6 − superhalogen anion results in a substantial electronic stability decrease (by 2.38-6.74 eV); (3) when the certain number of alkyl substituents is achieved, the PF 6−n (R) n − anions become thermodynamically unstable.

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“…11,12 Recent works reported by Skurski and co-workers have indicated that introducing a superhalogen-like substituent into organic molecules, e.g., hydrocarbon and amino acid, 16-18 would regulate these molecules electronic properties. [16][17][18] Therefore the electronic properties of the organic species could be regulated by superhalogens. That is to say, the organic molecules, of which the anionic forms are unstable, [10][11][12][20][21][22] will produce stable anions after introducing superhalogen- 55 like substituent.…”

Section: Introductionmentioning

confidence: 99%

“…[10][11][12] Albeit the F, Cl, and CN species are considered relatively effective oxidizing agents (due to their large electron affinities spanning the 3.40-3.90 eV range) [13][14][15] the resulting C 2 H 3 X, C 2 H 5 X, and C 6 H 5 X molecules (X = F, Cl, and CN) do not bind an excess electron to form electronically stable anions. 11,12 Recent studies reported by Skurski and co-workers have indicated that introducing a superhalogen-like substituent into organic molecules, e.g., hydrocarbons and amino acids, [16][17][18] would regulate the electronic properties of these molecules. These composite structures, 19 generated from the combination of organic molecules of small or even negative VDE with superhalogens, possess VDE values apparently higher than their organic parents.…”

Section: Introductionmentioning

confidence: 99%

“…That is to say, the organic molecules, of which the anionic forms are unstable, [10][11][12][20][21][22] will produce stable anions after introducing a superhalogen-like substituent. [16][17][18] Therefore the electronic properties of the organic species could be regulated by superhalogens. This type of regulation of the electronic properties of organic molecules may probably broaden the application potential of superhalogens 16,18 and thus it is highly worthy of subsequent systematic investigation.…”

Section: Introductionmentioning

confidence: 99%

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Is the regulation of the electronic properties of organic molecules by polynuclear superhalogens more effective than that by mononuclear superhalogens? A high-level ab initio case study

Bai

et al. 2015

Phys. Chem. Chem. Phys.

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The regulation of the electronic properties of organic molecules induced by polynuclear superhalogens is theoretically explored here for sixteen composite structures. It is clearly indicated by the higher vertical electron detachment energy (VDE) that polynuclear superhalogens are more effective in regulating the electronic properties than mononuclear structures. However, this enhanced regulation is not only determined by superhalogens themselves but also related to the distribution of the extra electron of the final composites. The composites, in which the extra electron is mainly aggregated into the superhalogen moiety, will possess higher VDE values, as reported in the case of C1', 7.12 eV at the CCSD(T) level. This is probably due to the fact that, compared with organic molecules, superhalogens possess stronger attraction towards the extra electron and thus should lead to lower energies of the extra electrons and to higher VDE values eventually. Compared with CCSD(T), the Outer Valence Green's Function (OVGF) method fails completely for composite structures containing Cl atoms, while MP2 results are generally consistent in terms of the relative order of VDEs. Actually if the extra electron distribution of the systems could be approximated by the HOMO, the results at the OVGF level will be consistent with the CCSD(T) results. Conversely, the difference in VDEs between OVGF and CCSD(T) is significantly large. Besides superhalogen properties, the structures, relative stabilities and thermodynamic stabilities with respect to various fragmentation channels were also investigated for all the composite structures.

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Amino acids form strongly bound anions when substituted with superhalogen ligands

Cited by 7 publications

References 33 publications

Electron affinity of modified benzene

Electron affinity of modified benzene

The PF₆₋_n(R)_n⁻anions (R = CH₃, C₂H₅;n= 0–6): the dependence of the electronic stability on the number of non-electronegative alkyl ligands

Is the regulation of the electronic properties of organic molecules by polynuclear superhalogens more effective than that by mononuclear superhalogens? A high-level ab initio case study

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Amino acids form strongly bound anions when substituted with superhalogen ligands

Cited by 7 publications

References 33 publications

Electron affinity of modified benzene

Electron affinity of modified benzene

The PF6−n(R)n−anions (R = CH3, C2H5;n= 0–6): the dependence of the electronic stability on the number of non-electronegative alkyl ligands

Is the regulation of the electronic properties of organic molecules by polynuclear superhalogens more effective than that by mononuclear superhalogens? A high-level ab initio case study

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The PF₆₋_n(R)_n⁻anions (R = CH₃, C₂H₅;n= 0–6): the dependence of the electronic stability on the number of non-electronegative alkyl ligands