Perylene Radical Cation Research Articles

Remarks on anisotropic rotational diffusion effects in the ESR spectra of radical cations generated on an acidic surface

The linewidth variations in the ESR hyperfine spectra of the radical cations of anthracene, perylene, and tetracene generated by adsorption on an acidic surface (silica–alumina) are analyzed in terms of the Freed–Fraenkel theory as modified to include anisotropic diffusion effects. The analysis is based on computer simulation of the observed experimental spectra. In the case of anthracene and perylene quite acceptable agreement is obtained if the diffusion tensor is chosen to have axial and near-axial symmetry, respectively, although a small amount of modulation of the isotropic hyperfine interactions may also be present in each case. The results are reviewed in terms of current theories of the nature of the adsorbent–adsorbate interaction on this type of surface. Similar calculations applied to tetracene failed to produce agreement between the simulated and experimental spectra and an additional spin relaxation mechanism involving electron transfer was included in the calculation. Although agreement was somewhat improved thereby, discrepancies remained. The tetracene results are reviewed in terms of the known redox behavior of the system.

The reduction of perylene radical cation by nucleophilic addition

The reduction of perylene radical cation by nucleophilic addition

ChemInform Abstract: SOME PROPERTIES OF AMMONIUM EXCHANGED TYPE L ZEOLITE

AbstractDie thermische Umwandlung des NH4L und ihr Einfluß auf die Acidität, die katalytische Aktivität und die Ladungsübertragungskapazität werden mit Hilfe der Pyridinadsorption (IR‐Spektroskopie), der Cumolcrackung (Mikroreaktormethode) sowie der Adsorption von SO2 und Perylen (EPR) untersucht.

ChemInform Abstract: MAGNETIC SUSCEPTIBILITY OF PERYLENE‐IODINE COMPLEX

Chemischer InformationsdienstVolume 7, Issue 35 Physical Organic Chemistry ChemInform Abstract: MAGNETIC SUSCEPTIBILITY OF PERYLENE-IODINE COMPLEX MINORU KINOSHITA, MINORU KINOSHITASearch for more papers by this authorHISAO KANDA, HISAO KANDASearch for more papers by this authorHIDEO AKAMATU, HIDEO AKAMATUSearch for more papers by this author MINORU KINOSHITA, MINORU KINOSHITASearch for more papers by this authorHISAO KANDA, HISAO KANDASearch for more papers by this authorHIDEO AKAMATU, HIDEO AKAMATUSearch for more papers by this author First published: August 31, 1976 https://doi.org/10.1002/chin.197635047AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume7, Issue35August 31, 1976 RelatedInformation

Magnetic Susceptibility of Perylene-Iodine Complex

Abstract The magnetic susceptibility of a highly conductive 2 : 3 charge-transfer complex of perylene with iodine has been examined as a function of temperature. The paramagnetic susceptibility, which was found to be nearly independent of temperature, is considered to be due only to the perylene cation radical.

Studies of chemistry of radical cations of perylene and tetracene by a flash-photolytic technique

Perylene radical cations (Pe[graphic omitted]) and pyromellitic dianhydride radical anions (PyAnh[graphic omitted]) are formed when acetonitrile solutions of the parent compounds are flash-irradiated with visible light and are annihilated by biomolecular combination (Rr= 7.6 × 109 1 mol–1 s–1) which does not form any new products; similar reactions are observed for tetracene (Tt) and an equilibrium Pe·++ Tt ⇌ Pe + T·+(K= 15) is established when a mixture of both hydrocarbons is used, the lifetime of radical cations being greatly increased by the addition of Fe3+(ClO4–)3 but not by the addition of AgClO4.

Some properties of ammonium exchanged type L zeolite

Various properties of ammonium exchanged type L zeolite have been studied. The deammoniation of NH4–L and the following formation of acidic centres were examined by infrared spectroscopy. Most of the hydroxyl groups and pyridinium ions formed interact with lattice oxygens through hydrogen bonding. The activity of NH4–L (33) for cumene cracking showed that deammoniation is complete around 350°C and that the dehydroxylation occurs between 500–600°C. The formation of sulphur dioxide anion radicals and perylene cation radicals revealed the charge transfer properties of the zeolite. NH4–L zeolite with a high degree of exchange is not thermally stable even at 450°C.

Solvation Shell Relaxation and Ion-Electron Recombination in Strongly Associated Solvents

The relaxation properties of the region in a solution in which there is strong interaction between the solute and solvent molecules (the cybotactic region) were studied with electron paramagnetic resonance spectroscopy used as the detection system. In the system under investigation, perylene radical cation was used as the solute, and either sulfuric acid or fluorosulfonic acid was used as the solvent. The properties studied were the solvent cage reorientation time and the ion-electron recombination time. Modulated light of a known wavelength distribution was used to irradiate the sample and synchronize a lock-in detector, which was used to detect the light-induced effects, to the light modulation frequency. Signal averaging techniques were used so that accurate values of the output as functions of the sample temperature, irradiation light wavelength, and irradiation light modulation frequency were obtained. Two extreme model systems were used to interpret the light-induced signal data, a reversible and an impulse model. A range of times was specified for the solvent cage reorientation and ion-electron recombination as a function of the sample temperature. In sulfuric acid, the cage reorientation time varies from 1176 μsec at 6°C to 99 μsec at 77°C, while the ion-electron recombination time varies from 649 to 42 μsec. The temperature range studied for fluorosulfonic acid was −36–95°C. In this range, the cage reorientation time varied from 857 to 81 μsec and the ion-electron recombination from 815 to 35 μsec. Over the temperature ranges studied, the intermediate coupling constant for the perylene radical cation increased from 13.7 to 224 mG in sulfuric acid and 19.7 to 345 mG in fluorosulfonic acid.

Electrochemiluminescence of Energy‐Deficient Systems II. The Role of Excimer Formation in the Pure Perylene System

AbstractThe reaction enthalpy Δ H of the chemiluminescent electron‐transfer reaction between perylene radical cations and anions has been estimated from electrochemical measurements. The comparison of H with the energies of the excited states of perylene leads to the conclusion that excited singlet molecules, the emission of which is observed, cannot be formed directly; rather excited triplets are produced in the electron‐transfer reaction which yield excited singulets via triplet‐triplet annihilation. This mechanism is confirmed by the analysis of the ecl intensity‐time curves. The long‐wavelength component occuring in the ecl spectrum of perylene is ascribed to excimer emission in agreement with the experimental results. These suggest the assumption that the intensity ratio of the long‐wavelength component to the fluorescent component is determined by the fact that perylene triplets—dependent on electrolysis time ‐ are quenched by excess radical ions in the reaction zone; the excimers, however, are not.

Electrochemiluminescence of Energy‐Deficient Systems I. Triplet‐Triplet‐Annihilation in Mixed Systems

AbstractIt is shown by means of electrochemical experiments that the chemiluminescent electron‐transfer reaction between perylene radical anions and tri‐p‐tolylamine radical cations and between perylene radical cations and benzil radical anions, respectively, are energy‐deficient, i. e. the reaction enthalpy is smaller than the energy of the lowest excited singlet state of perylene, the fluorescence emission of which is observed. This result implies the formation of perylene molecules in the triplet state in the course of the electron‐transfer reaction with subsequent triplet‐triplet annihilation yielding perylene molecules in the excited singlet state. The triplet mechanism is confirmed by the analysis of the light intensity‐time curves.

Ion radicals. XXIII. Reactions of the perylene cation radical

Ion radicals. XXIII. Reactions of the perylene cation radical

Computer Simulation of the ESR Spectra of the Naphthalene, Anthracene, and Perylene Radical Cations in a Polycrystalline Medium

Computer simulation of ESR spectra in polycrystalline environments is extended to the case of free radicals in which the unpaired spin is extensively delocalized. An approximate model is proposed for the anisotropic effects (g tensor, dipolar hyperfine tensor, component shape and width). This model is tested on the spectra of anthracene and perylene radical cations in boric-acid glass [G. Vincow and P. M. Johnson, J. Chem. Phys. 39, 1143 (1963)]. The spectral structure is reproduced by the calculations. A principal application of this simulation procedure is the extraction of values of the Fermi contact hyperfine splittings in cases for which these have not been measured. As an illustration, the powder spectrum of the naphthalene cation radical is considered, yielding | a1H | = 5.4 ± 0.3 G and | a2H | = 1.62 ± 0.3 G. In addition calculations are performed which indicate the sensitivity of the simulated spectra to variations in values of the parameters of the model.

Antimony halides as solvents. Part VII. Magnetic susceptibility measurements on perylene radical-cations

The oxidation of perylene in molten antimony trichloride has been studied by the Gouy method. Radical-cation formation is complete at low concentrations, but dimerisation, polymerisation, or formation of a chloroantimonate complex occurs at higher concentrations (the nature of the reaction depends on the oxidant). Perylene is only partially oxidised in the solid 1 : 1 complex with antimony pentachloride.

Electron Spin Resonance of Radical Cations Produced by the Oxidation of Aromatic Hydrocarbons with SbCl5

Electron spin resonance (ESR) studies have been made of radical cations prepared by the oxidation of 24 aromatic hydrocarbons with SbCl5 in CH2Cl2 solvent. The transfer of reagents, reactions, and ESR measurements were carried out at temperatures below −78°C in the absence of air. The stability of the radicals in solution, and the resolution of ESR hyperfine structure, depended critically on temperature and on the concentrations of hydrocarbon and SbCl5. The coupling constants for the ESR spectra of the radical cations of perylene, anthracene, 9,10-dimethylanthracene, and naphthacene were essentially identical to those for the respective ions in H2SO4. The ESR spectra for the radical cations of pyrene, naphthalene, dibenzo-(a,c)triphenylene,Δ9,9′-bifluorene, and tetraphenylethylene have also been reduced to coupling constants. The positive radical ion resulting from the oxidation of naphthalene is a symmetrical dimer with the unpaired electron divided equally between the two molecules. The generality of McConnell's relationship aH=Qρ was examined by comparing experimental coupling constants with Hückel spin densities for available radical anion and cation data. A least-squares fitting procedure yielded Q=28.6 for anions and Q=35.7 for cations. Quantitative comparisons were made between experimental coupling constants and those computed from the Colpa—Bolton and Giacometti—Nordio—Pavan theories. Both theories were found to account appropriately for the differences in magnitude between the coupling constants for aromatic negative and positive ions.

Acidities of silica-alumina catalysts

It is generally accepted that the chemisorption of triphenylmethane on silica-alumina involves hydride ion abstraction and constitutes evidence for a few (5 × 1012/cm2) strong Lewis acid sites. Observations contrary to this interpretation include (1) about ten molecules of NH3 or n-butylamine per “Lewis site” are required to poison the reaction; (2) protonic acids mounted on silica also catalyze this reaction; (3) 90% or more of the chemisorbed trityl ion is recovered as triphenylcarbinol, not triphenylmethane; (4) the rate of formation of trityl ions is strongly accelerated by light; (5) the generation of trityl ions by SiO2 + BF3 does not proceed at a significant rate in the dark, and triphenylcarbinol is a product of the light reaction.The evidence suggests that triphenylmethane is oxidized to triphenylcarbinol, followed by reaction with a Bronsted acid to generate the trityl ion. In support of this interpretation, Ph3CH and Ph3COH give substantially the same endpoint when used as indicators in the titration of catalyst acidity with n-butylamine.Evidence is also presented that in the reaction of perylene with silica-alumina to form the perylene cation radical, Bronsted sites catalyze the reaction with some form of chemisorbed oxygen which acts as the electron acceptor. The spin concentration is therefore not a measure of the number of strong Lewis acid sites.

The reaction of triphenylmethane and perylene with silica-alumina the nature of the acid sites

It is generally accepted that the chemisorption of triphenylmethane on silica-alumina involves hydride ion abstraction and constitutes evidence for a few (5 × 10 12/cm 2) strong Lewis acid sites. Observations contrary to this interpretation include (1) about ten molecules of NH 3 or n-butylamine per “Lewis site” are required to poison the reaction; (2) protonic acids mounted on silica also catalyze this reaction; (3) 90% or more of the chemisorbed trityl ion is recovered as triphenylcarbinol, not triphenylmethane; (4) the rate of formation of trityl ions is strongly accelerated by light; (5) the generation of trityl ions by SiO 2 + BF 3 does not proceed at a significant rate in the dark, and triphenylcarbinol is a product of the light reaction. The evidence suggests that triphenylmethane is oxidized to triphenylcarbinol, followed by reaction with a Bronsted acid to generate the trityl ion. In support of this interpretation, Ph 3CH and Ph 3COH give substantially the same endpoint when used as indicators in the titration of catalyst acidity with n-butylamine. Evidence is also presented that in the reaction of perylene with silica-alumina to form the perylene cation radical, Bronsted sites catalyze the reaction with some form of chemisorbed oxygen which acts as the electron acceptor. The spin concentration is therefore not a measure of the number of strong Lewis acid sites.