Real-time TD-DFT study on the dioxygen/superoxide radical charge transfer reaction

Workman, Aron

doi:10.1016/j.comptc.2017.08.020

Cited by 5 publications

(3 citation statements)

References 39 publications

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“…The SOMO–HOMO inversion in O 2 •– was previously indicated in other theoretical works but not discussed. 28 , 29 The spin density distribution plot of O 2 •– 4H 2 O shows that spin is equal on each oxygen with the MO π* in nature, see Figure 2 . Using EPR, Sevilla et al 25 measured the O-17 hyperfine coupling constants (HFCCs) of O 2 •– .…”

Section: Resultsmentioning

confidence: 98%

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SOMO–HOMO Level Inversion in Biologically Important Radicals

Kumar

Sevilla

2017

J. Phys. Chem. B

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Conventionally, the singly occupied molecular orbital (SOMO) of a radical species is considered to be the highest occupied molecular orbital (HOMO), but this is not the case always. In this study, we considered a number of radicals from smallest diatomic anion radicals such as superoxide anion radical to one-electron oxidized DNA related base radicals that show the SOMO is energetically lower than one or more doubly occupied molecular orbitals (MOs) (SOMO–HOMO level inversion). The electronic configurations are calculated employing the B3LYP/6-31++G** method, with the inclusion of aqueous phase via the integral equation formalism of the polarized continuum model solvation model. From the extensive study of the electronic configurations of radicals produced by one-electron oxidation or reduction of natural-DNA bases, bromine-, sulfur-, selenium-, and aza-substituted DNA bases, as well as 20 diatomic molecules, we highlight the following important findings: (i) SOMO–HOMO level inversion is a common phenomenon in radical species. (ii) The more localized spin density in σ-orbital on a single atom (carbon, nitrogen, oxygen, sulfur, or selenium), the greater the gap between HOMO and SOMO. (iii) In species with SOMO–HOMO level inversion, one-electron oxidation takes place from HOMO not from the SOMO, which produces a molecule in its triplet ground state. Oxidation of aqueous superoxide anion producing triplet molecular oxygen is one example of many. (iv) These results are for conventional radicals and in contrast with those reported for distonic radical anions in which SOMO–HOMO gaps are smaller for more localized radicals and the orbital inversions vanish in water. Our findings yield new insights into the properties of free radical systems.

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Section: Resultsmentioning

confidence: 98%

“…•− was previously indicated in other theoretical works but not discussed. 28,29 The spin density distribution plot of O 2…”

Section: •−mentioning

confidence: 99%

SOMO–HOMO Level Inversion in Biologically Important Radicals

Kumar

Sevilla

2017

J. Phys. Chem. B

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“…In the reaction mechanisms shown in Scheme 3, Li 2 CO 3 is first ionized into the lithium ion and carbonate anion (1), then the carbonate anion is hydrolyzed into the hydroxide ion and bicarbonate anion (2), and the bicarbonate is further hydrolyzed to produce OH − (3), which makes the solution alkaline and pH increases. In addition, in the presence of air, the aqueous solution undergoes an oxygen reduction reaction 52,53 under the action of an electric field to generate superoxide radicals (4). The superoxide radicals continue to react with water in an alkaline medium to generate the hydrogen peroxide anion (HO 2− ), while oxygen is released (5).…”

Section: Electrochemical Behavior Of Lithium Carbonatementioning

confidence: 99%