A stable, highly oxidizing radical cation

2020 ◽  
Vol 44 (42) ◽  
pp. 18138-18148
Author(s):  
N. Harsha Attanayake ◽  
Aman Preet Kaur ◽  
T. Malsha Suduwella ◽  
Corrine F. Elliott ◽  
Sean R. Parkin ◽  
...  
Keyword(s):  
Ionization Potential ◽  
Radical Cation ◽  
Oxidation Potential ◽  
Adiabatic Ionization Potential ◽  
Half Wave

Changes in adiabatic ionization potential and half wave oxidation potential with ortho and para substitution on an N-alkylated phenothiazine.

Products from photochemical reactions and electrochemical oxidation of methylenecyclopropane

1997 ◽  
Vol 75 (12) ◽  
pp. 1795-1809 ◽  
Author(s):  
H.J.P. de Lijser ◽  
T. Stanley Cameron ◽  
Donald R. Arnold
Keyword(s):  
Electron Transfer ◽  
Ionization Potential ◽  
Radical Cation ◽  
Photoinduced Electron Transfer ◽  
Nucleophilic Addition ◽  
Major Product ◽  
Oxidation Potential ◽  
Photochemical Reactions ◽  
Tert Butyl ◽  
Adiabatic Ionization Potential

The reactivity of methylenecyclopropane (MCP, 1) and its radical cation (1+•) have been studied in the presence and absence of a nucleophile (methanol). Photochemical reactions of 1 in the presence of an electron-acceptor (1,4-dicyanobenzene, 6) and a codonor (biphenyl, 7) in acetonitrile (with and without methanol present) or chloroform lead to cycloadditions (ortho, meta, and para; products 12–17) rather than products from photoinduced electron transfer (PET). Based on the measured (cyclic voltammetry, CV) oxidation potential, using the Weller equation, electron transfer (ET) was predicted to occur. It was shown that the measured oxidation potential of 1 represents the adiabatic ionization potential. For PET processes the value for the vertical ionization potential must be used. Electrochemical (EC) generation of 1+• without a nucleophile present results in the formation of one major product: tert-butyl acetamide (25). A series of rearrangements leading to the tert-butyl cation is proposed. Addition of a nucleophile (methanol) to the mixture leads to the formation of 3-methoxy-2-(methoxymethyl)-1-propene (26). This product may arise from trapping of the initially formed ring-opened (trimethylenemethane) radical cation (1a+•), which undergoes a second oxidation and nucleophilic addition (ECE). Keywords: methylenecyclopropane, radical cation, photochemistry, electrochemistry, photocycloaddition.

Radical ions in photochemistry. 21. The photosensitized (electron transfer) tautomerization of alkenes; the phenyl alkene system

1989 ◽  
Vol 67 (4) ◽  
pp. 689-698 ◽  
Author(s):  
Donald R. Arnold ◽  
Shelley A. Mines
Keyword(s):  
Hydrogen Bond ◽  
Electron Transfer ◽  
Radical Cation ◽  
Radical Anion ◽  
Phenyl Group ◽  
Oxidation Potential ◽  
Original Position ◽  
Acetonitrile Solution ◽  
Steric Interaction ◽  
Ambident Anion

Alkenes, conjugated with a phenyl group, can be converted to nonconjugated tautomers by sensitized (electron transfer) irradiation. For example, irradiation of an acetonitrile solution of the conjugated alkene 1-phenylpropene, the electron accepting photosensitizer 1,4-dicyanobenzene, the cosensitizer biphenyl, and the base 2,4,6-trimethylpyridine gave the nonconjugated tautomer 3-phenylpropene in good yield. Similarly, 2-methyl-1-phenylpropene gave 2-methyl-3-phenylpropene, and 1-phenyl-1-butene gaveE- and Z-1-phenyl-2-butene. The reaction also works well with cyclic alkenes. For example, 1-phenylcyclohexene gave 3-phenylcyclohexene, and 1-(phenylmethylene)cyclohexane gave 1-(phenylmethyl)cyclohexene. The proposed mechanism involves the initial formation of the alkene radical cation and the sensitizer radical anion, induced by irradiation of the sensitizer and mediated by the cosensitizer. Deprotonation of the radical cation assisted by the base gives the ambident radical, which is then reduced to the anion by the sensitizer radical anion. Protonation of the ambident anion at the benzylic position completes the sequence. Reprotonation at the original position is an energy wasting step. Tautomerization is driven toward the isomer with the higher oxidation potential, which is, in the cases studied, the less thermodynamically stable isomer. The regioselectivity of the deprotonation step is dependent upon the conformation of the allylic carbon–hydrogen bond. The tautomerization of 2-methyl- 1-phenylbutene gave both 2-phenylmethyl-1-butène and 2-methyl-1-phenyl-2-butene (E and Z isomers), while 2,3-dimethyl- 1-phenylbutene gave only 3-methyl-2-phenylmethyl-1 -butene. In the latter case, steric interaction of the methyls on the isopropyl group prevents effective overlap of the tertiary carbon–hydrogen bond with the singly occupied molecular orbital, thus inhibiting deprotonation from this site. Keywords: photosensitized, electron transfer, alkene, tautomerization, radical cation.

The first adiabatic ionization potential of Ar2

1997 ◽  
Vol 107 (24) ◽  
pp. 10819-10822 ◽  
Author(s):  
R. Signorell ◽  
A. Wüest ◽  
F. Merkt
Keyword(s):  
Ionization Potential ◽  
Adiabatic Ionization Potential

Dynamics of the transient species generated upon photolysis of diarylmethanes within zeolites — Deprotonation and oxidation reactions

2005 ◽  
Vol 83 (9) ◽  
pp. 1637-1648 ◽  
Author(s):  
Suzanne Shea ◽  
Norman P Schepp ◽  
Amy E Keirstead ◽  
Frances L Cozens
Keyword(s):  
Radical Cation ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Radical Cations ◽  
Laser Flash ◽  
Oxidation Potential ◽  
Oxidation Reactions ◽  
Oxidation Potentials ◽  
Multistep Process ◽  
Acid Zeolites

The oxidation of diarylmethanes is a multistep process involving initial formation of a radical cation, deprotonation of the radical cation to the radical, and oxidation of the radical to the carbocation. The dynamics and efficiency of the last two steps in this process, namely deprotonation and oxidation, in acidic zeolites and non-acid zeolites are examined in the present work as a function of the acidity of the diarylmethane radical cations and the oxidation potential of the diarylmethyl radicals. Our results indicate that rate constants for deprotonation strongly depend on the acidity of the radical cations, but not on the composition of the zeolites. In addition, oxidation of the radicals to the diarylmethyl cations is strongly dependent on both the oxidation potential of the radicals and the oxidizing ability of the zeolite. This dependence allows oxidation potentials of the zeolites to be estimated.Key words: radical cations, carbocations, zeolites, laser flash photolysis.

Photochemical nucleophile–olefin combination, aromatic substitution (photo-NOCAS) reaction. Part 6: methanol, nonconjugated dienes, and 1,4-dicyanobenzene

1994 ◽  
Vol 72 (2) ◽  
pp. 415-429 ◽  
Author(s):  
Donald R. Arnold ◽  
Kimberly A. McManus ◽  
Xinyao Du
Keyword(s):  
Electron Transfer ◽  
Double Bond ◽  
Radical Cation ◽  
Oxidation Potential ◽  
Aromatic Substitution ◽  
Double Bonds ◽  
Excited Singlet ◽  
Reaction Conditions ◽  
Methanol Solutions ◽  
Cyclic Adducts

Irradiation, through Pyrex, of an acetonitrile–methanol (3:1) solution of 1,4-dicyanobenzene (1) and 1,5-hexadiene (9) leads to formation of ortho and meta cyclic adducts (13–16) arising from the intermediate exciplex. There was no evidence for interaction between the two double bonds of this nonconjugated diene. The oxidation potential of 9 is high enough (> 3 V vs. sce) to preclude single electron transfer (SET); no photo-NOCAS products are formed. Similar irradiation of acetonitrile–methanol solutions of 1 and 2-methyl-1,5-hexadiene (10) does yield a photo-NOCAS product (17); reaction occurs only on the more heavily substituted double bond. The additional substitution on the double bond lowers the oxidation potential (2.70 V vs. sce) of this diene to the point where SET from 10 to the excited singlet state of 1 can occur. In this case, no cycloaddition products are formed; the exciplex is quenched by electron transfer. There was no evidence for interaction between the two double bonds of the initially formed radical cation 10+•, or between the terminal double bond and the β-alkoxyalkyl radical of the intermediate leading to the photo-NOCAS product. The photo-NOCAS product (19) was also formed when 2,5-dimethyl-1,5-hexadiene (11) was subjected to these reaction conditions. In this case, when biphenyl (4) was added as a codonor, in addition to the photo-NOCAS product, products (21cis and trans) resulting from cyclization of the initially formed acyclic radical cation 11+• to give the 1,4-dimethylcyclohexane-1,4-diyl radical cation were also observed. This 1,6-endo, endo cyclization of 11+• must be rapid enough to compete with reaction with methanol. There was no evidence for cyclization (neither 1,4-exo nor 1,5-endo) of the intermediate β-alkoxyalkyl radical. When the radical cation of 2,5-dimethyl-1,4-hexadiene (12+•) is generated under these reaction conditions, photo-NOCAS products 22 and 23 are formed at the more heavily substituted double bond, along with the conjugated tautomer 2,5-dimethyl-2,4-hexadiene (24). The mechanisms for these transformations are discussed.

scholarly journals New determination of the adiabatic ionization potential of the BaOH radical from laser photoionization-molecular beam experiments and ab initio calculations

2012 ◽  
Vol 136 (6) ◽  
pp. 064303 ◽  
Author(s):  
Maximiliano Rossa ◽  
Iván Cabanillas-Vidosa ◽  
Gustavo A. Pino ◽  
Juan C. Ferrero
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Ionization Potential ◽  
Molecular Beam ◽  
Adiabatic Ionization Potential ◽  
Laser Photoionization

Radikalionen, 62 [ 1—3]Bis(dimethyIamino)dibenzoheptafulven-Radikalkation /Radical Ions, 62 [1—3]Bis(dimethylamino)dibenzoheptafulvene Radical Cation

1984 ◽  
Vol 39 (6) ◽  
pp. 771-777 ◽  
Author(s):  
Hans Bock ◽  
Bernhard Roth ◽  
Jörg Daub
Keyword(s):  
Ionization Potential ◽  
Radical Cation ◽  
Ground State ◽  
Title Compound ◽  
Valence Electron ◽  
Esr Spectra ◽  
Vertical Ionization Potential ◽  
Radical Ions ◽  
Mndo Calculations ◽  
Multiplet Signal

AbstractThe neutral title compound, 8,8-bis(dimethylamino)dibenzo-[a,d]-heptafulvene, exhibits a first vertical ionization potential of only 6.98 eV and, therefore, can also be oxidized by AlCl3 in H2CCl2 solution. The radical cation generated shows a complex multiplet signal pattern, which is assigned based on additional ENDOR measurements. The photoelectron (PE) and ESR spectra of the 112 valence electron molecule are interpreted by “pararneter-optimized” HMO and by geometry-optimized MNDO calculations, which both suggest a non-planar π-type ground state with most of the charge and the spin distributed over the dibenzoheptatriene part of the radical cation.

scholarly journals Explicit solvent simulations of the aqueous oxidation potential and reorganization energy for neutral molecules: gas phase, linear solvent response, and non-linear response contributions

2015 ◽  
Vol 17 (22) ◽  
pp. 14811-14826 ◽  
Author(s):  
Jennifer J. Guerard ◽  
Peter R. Tentscher ◽  
Marianne Seijo ◽  
J. Samuel Arey
Keyword(s):  
Gas Phase ◽  
Ionization Energy ◽  
Linear Response ◽  
Reorganization Energy ◽  
Oxidation Potential ◽  
Adiabatic Ionization Potential ◽  
Explicit Solvent ◽  
Non Linear ◽  
Aqueous Oxidation ◽  
Adiabatic Ionization Energy

Explicit solvent simulations are used to partition the aqueous adiabatic ionization potential (AIEaq) into the gas phase adiabatic ionization energy (AIEgas), linear solvent response (ΔΔGLRAsolv), and non-linear solvent response (ΔΔΔGnon-LRsolv) contributions.

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