Phenalenyl Radical Research Articles

Preparation of 4-thia-10b-azaindeno[2,1,7-lma]fluorenes

The salt 2 condenses with dimethylformamide in acetic anhydride giving the Vilsmeier salt 3. This is cyclised to the parent 4-thia-10b-azaindeno[2,1,7-lma]fluorene 4 by triethylamine in dimethylformamide. When the salt 2 is heated in acetic anhydride in the presence of triethylamine the green thiacyclazine derivative 5 is isolated. Introduction Cycl[3.3.3]azine 1 and its derivatives have been studied extensively1 in connection with their structural relationship to the phenalenyl cation, anion and radical (C+, C–, C• respectively in place of N in 1).2 Numerous novel heterocyclic systems are possible, but as yet unknown, in which a =CH– or –CH=CH– moiety in 1 is replaced by a heteroatom unit. We report here syntheses of sulfur-containing analogues of 1, in which a –CH=CH– moiety is replaced by sulfur, starting from the indeno[2,1-d]pyrido[2,1-b]thiazolium salt 2.

A Magnetic Resonance Study of Complex Formation between the Neutral Phenalenyl Radical and Alkali Metal Ions in Dilute Alcohol Solutions

In previous work from our laboratories we have characterized the molecular motion of phenalenyl in the supercage of cation-exchanged X- and Y-zeolites using continuous wave−electron paramagnetic resonance (CW-EPR) and pulsed-EPR techniques. The trends in activation energies with cation size and Lewis acidity and in EPR line widths provided circumstantial evidence for a weak covalent interaction between the neutral phenalenyl π-system and the cations. This work on phenalenyl and alkali metal cations in solution provides 7Li nuclear magnetic resonance (NMR) and CW-EPR spectroscopic evidence for this type of interaction. Moreover, to our knowledge it is the first example of a neutral radical−alkali metal ion complex in solution. In rigorously dried alcohol solutions this interaction results in the formation of a complex between neutral phenalenyl and Li+ or Na+, which is in equilibrium with solvated phenalenyl and the respective cation. The forward and reverse rates for this equilibrium for Li+ and phenaleny...

Electronic Structure of a Stable Phenalenyl Radical as Studied by ESR/ENDOR, Paramagnetic NMR Spectroscopy and SQUID Measurements

We have studied magnetic properties and electronic structures of a novel persistent neutral radical, 2,5,8-tri-tert-butylphenalenyl(2), which is the first example of alternant hydrocarbon π-radical isolated in the crystalline state. The observed magnetic susceptibilities of polycrystalline sample 2 were reproduced by assuming the thermal equilibrium between singlet ground state and excited triplet state of the dimer (2J/k B = −2×103 K) with traces of paramagnetic impurity molecules (0.3mol%). The π-spin density distribution of radical 2 was determined by liquid-phase cw-ESR, 1H-ENDOR/TRIPLE, and paramagnetic 1H-NMR measurements. The origin of the large inter-molecular antiferromagnetic interaction in the crystal 2 was explained by an occurrence of effective SOMO-SOMO overlap between the two radicals on the six equivalent α-positions with large positive spin densities of the carbon sites.

Electronic structure of a stable phenalenyl radical in crystalline state as studied by SQUID measurements, cw-ESR, and 13C CP/MAS NMR spectroscopy

A neat single crystal of phenalenyl radical was obtained for the first time by introducing the substituent group of tert-butyl X-ray structure analysis of the crystal of 2,5,8-tri- tert-butylphenalenyl( 2) showed that the two planar radicals face each other with inversion symmetry and are dimerized in the monoclinic crystal. This is supported by the magnetic susceptibility(χ) measurement of the crystalline solid state of 2 The observed temperature dependence of χT was reproduced by assuming the thermal equilibrium between a singlet ground state and excited triplet state of the dimer (2 J/k B = −2000K) with traces of paramagnetic impurity molecules (0.3mol%). The electronic structure of the radical dimer in the crystalline state has been identified also by single-crystal ESR and 13C CP/MAS NMR measurements. The origin of the large antiferromagnetic interaction is discussed in terms of both the experimentally determined π-spin density distribution of monomer radicals and π MO calculations.

Bimolekulare Radikalbildung durch H‐Transfer, 2. H‐Transferreaktionen mit Phenalen

Bimolecular Formation of Radicals by H‐Transfer, 2[1]. – H‐Transfer Reactions of PhenaleneThe uncatalysed H transfer from phenalane (7) to α1‐methyl‐styrene (2) and the selfreaction (d) of phenalene (7) are quantitative transformations in the presence of an excess of 9,10‐dihydroanthracene (1) (DHA) in diphenyl ether at 200–250°C. In this system phenalene (7) is consumed only in reaction (d) because the phenalenyl radicals (9) are captured by DHA (1) to give phenalene (7) and 9,10‐dihydroanthryl radicals (3). The latter disproportionate rapidly. Accordingly, phenalene (7) acts as a catalyst for the hydrogenation of α1‐methylstyrene (2) by DHA (1). The activation parameters of the two reactions (e) and (d) were obtained from kinetic experiments between 200–250°C. They allow the determination of the CH bond enthalpy δHdiss of phenalene (7) (65.3 kcal mol–1) at the methylene position.

MECHANISTIC CONSIDERATIONS CONCERNING THE STABILITY TOWARDS DIOXYGEN OF EVOLUTIVE FUELS.

Abstract The interaction of phenalenonc and 2-methylindole in presence of stoechiomctric amounts of paratoluenesulfonic acid in methanol under argon, yields twelve compounds which have been spectroscopically characterised. Seven compounds or sets of compounds could be scpareted by flash chromatography. Phenalene 4. and phenalanone 8 result from a disproportionalion reaction of a key intermediate 18. 2-Methylindolylphenalene 5 and bis(2-methyl)indolylphenalene 6 and 7 exist under the form of a complex mixture of lauiomers. 2-Methylindolylphenalanones 9 and 10. 2-methylindolylphenalenones 11. 12. 1 3. and bis(2-methylindolyl)phenalenones 14 and 15. could also be isolated from the reaction mixture. In presence of air and light compounds 5, 6, and 7. oxidize into 11, 12, 13, 14, and 15 via the corresponding phenalenyl radical. The mechanism of formation and interconversion of these products is discussed and experimentally supported. The peculiar reactivity of the phenalenic derivatives is analysed and it is suggested that such structures are present in asphaltenes. An hypothesis about their genesis is proposed.

ChemInform Abstract: Synthesis and Characterization of Phenalenyl Cations, Radicals, and Anions Having Donor and Acceptor Substituents: Three Redox States of Modified Odd Alternant Systems.

AbstractThe phenalenes (V) are prepared following a known route.

E.s.r. characterization of phenalenyl radicals in various fuel samples

Various fuel samples were studied by e.s.r. spectroscopy to identify and quantify free radicals and molecules containing unpaired electrons. The 298 K spectra from various heavy fuel samples were characteristic of vanadyl porphyrins. In addition, a sharp intense peak near g = 2 was assigned to the free radicals that are always observed in the asphaltenes. Two kinds of e.s.r. spectra were observed among the gas oil samples: the straight run gas oil showed a single peak close to g = 2, while the light cycle oil (LCO) spectra were typical of the phenalenyl radical. The pyrolysis fuels exhibited a single resonance line attributed to an organic radical ( g = 2), and the mixed samples gave spectra similar to those of the heavy fuels. The data obtained by quantitative analysis of the unpaired electrons in fuel and gas oil samples are described. The concentration of phenalenyl radicals in LCO was found to decrease with time and with heating.

Synthesis and characterization of phenalenyl cations, radicals, and anions having donor and acceptor substituents: three redox states of modified odd alternant systems

Les resultats obtenus ont une importance fondamentale pour l'exploration de nouveaux materiaux organiques possedant les proprietes electriques et magnetiques interessantes

The hydrogenolysis of diarylmethane: Mechanism for hydrogen transfer from solvents and additive effects of hydrogen shuttlers and organic radical sources

The thermal decomposition of the diarylmethane in hydrogen-donor solvents proceeds via the ipso-addition of a hydrogen atom transferred from the solvent. This reaction is slow in tetralin at temperatures of 430–460 °C, but it is promoted by a binary solvent system composed of tetralin and dibenzyl (20:1 molar ratio), and its ability to donate hydrogen is comparable with that of 9,10-dihydroanthracene. The additive effect of 1H-phenalene as a source of phenalenyl radical is half that of dibenzyl. The addition of a hydrogen shuttler such as anthracene and phenanthrene to tetralin also promotes the above reaction, but their additive effect is modest, compared with the hydrogen-donating abilities of the corresponding dihydro-derivatives.

Temperature dependent site structure of the phenalenyl radical in n-pentane and n-hexane shpol'skii matrices

The temperature dependence of the intensities of the sites in the Shpol'skii spectrum of the phenalenyl radical in n-hexane and n-pentane has been investigated. It appears that the site populations follow a Boltzmann distribution, pointing to the existence of a dynamic equilibrium between the sites. The temperature dependence can be explained by taking Jahn-Teller effects on the D 1 state of the radical into account.

Potentially conducting organometallic systems: the stibaphenalenyl series

Substituting some carbon atoms by antimony in the network of the odd alternate hydrocarbon phenalenyl (C/sub 13/H/sub 9/) radical can lead to a variety of new molecules. These molecules are investigated theoretically by using extended Hueckel computations, which point to a high potential of the compounds to be good organometallic conductors. Two main features are characteristic of all the members of the series: (a) the molecules exhibit an inherent propensity to form infinite stacks that are driven by strong intermolecular Sb---Sb bonding, and (b) the band structure of the stacks exhibits a few bands that are all less than half-filled. Each such band, by itself, may be conceived to arise from stacking of partially oxidized (doped) donors. The stibaphenalenyl stacks meet thereby the two main requirements of the highly conducting organic metals.

Electron paramagnetic resonance of pyrolysed dihydronaphthalenes

The hyperfine e.p.r. spectra observed for the pyrolysis products of 1,2- and 1,4-dihydronaphthalenes are re-examined. It is concluded that the spectra arise from the phenalenyl radical, rather than the dihydronaphthyl radical as suggested by previous workers.

Jahn-Teller effect in highly resolved optical spectra of the phenalenyl radical

Highly resolved emission and excitation spectra of phenalenyl are reported. Our semiempirical calculations predict E″ symmetry for the lowest excited state. Indeed, Jahn-Teller effects are observed. Force field calculations have been performed to determine the symmetries of vibrations visible in the spectra. The Jahn-Teller coupling is analysed with a scheme of Sloane and Silbey.

FREE RADICALS FORMED IN HYDROTREATED COAL LIQUID AND INFLUENCE OF OXYGEN

ABSTRACT The behavior of radicals formed in hydrotreated coal liquid with heat treatment and the influence of oxygen have been investigated by electron spin resonance (e.s.r.) spectroscopy. A set of e.s.r. spectral lines identified as phenalenyl radical appears from 50°C as the oil is heated in argon atmosphere. The radical concentration is enhanced with temperature, reaches a maximum between 130 and 150°C and then decreases at higher temperatures. The radical is very stable even at 200°C for the sample hydrotreated under mild condition, whereas the radical in the sample treated under severe conditions disappears drastically from 150°C. When oxygen is introduced in the oil, the radical is converted into semiquinone and/or aryloxy radicals and stable molecules. The treatment in the presence of oxygen at higher temperatures is considered to accompany the formation of other aryloxy radicals by the reaction of aromatic hydrocarbons and oxygen.

ChemInform Abstract: THE RADICAL IONS OF NAPHTHO(1,8‐CD)‐(1,2,6)THIADIAZINE AND SOME OF ITS DERIVATIVES

AbstractDie ESR‐Spektren der nach üblichen Methoden erzeugten Radikalkationen und ‐anionen der Titelverbindungen (Ia) und (Ib) sowie der Radikalanionen von (Ic) sind abgebildet und werden diskutiert.

The Radical Ions of Naphtho [1,8‐cd]‐[1,2,6]thiadiazine and Some of Its Derivatives

AbstractThe radical cations and anions of naphtho [1,8‐cd]‐[1,2,6]thiadiazine (1) and 6,7‐dihydroacenaphtho [5, 6‐cd]‐[1,2,6]thiadiazine (2), as well as the radical anion of acenaphtho [5, 6‐cd]‐[1,2,6]thiadiazine (3) have been characterized by ESR. spectroscopy. The π‐spin distributions in the radical cations \documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\oplus \atop \dot{}}$\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ 2^{\oplus \atop \dot{}}$\end{document} strongly resemble those in the iso‐π‐electronic phenalenyl radical. A prominent feature of the radical anions \documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\ominus \atop \dot{}}$\end{document}, \documentclass{article}\pagestyle{empty}\begin{document}$ 2^{\ominus \atop \dot{}}$\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ 3^{\ominus \atop \dot{}}$\end{document} is the substantial localization of the π‐spin population on the thiadiazine fragment. These findings are satisfactorily accounted for by HMO models using conventional heteroatom parameters.

Proton, deuteron, and carbon-13 ENDOR studies of phenalenyl radicals in nematic and smectic mesophases of liquid crystals

Proton, deuteron, and carbon-13 ENDOR studies of phenalenyl radicals in nematic and smectic mesophases of liquid crystals

Esr and endor studies of partially deuterated and chlorinated phenalenyls : New synthetic pathways

A variety of partially chlorinated and deuterated phenalenyl radicals has been produced by the reaction of the respective acenaphthylenes with chloroform as a carbenoid precursor and via thermal decomposition of some mercury carboxylates. By ESR and ENDOR-in-solution measurements the effectiveness of the different reaction paths to specifically substituted compounds has been investigated.

Photolysis of 2,2-Diethoxy-2,3-dihydrophenalene-1,3-dione

Abstract Irradiation of 2,2-diethoxy-2,3-dihydrophenalene-1,3-dione (6) with a pyrex-filtered high-pressure Hg arc lamp afforded acetaldehyde, 2-ethoxy-3-hydroxyphenalene-1-one (7) and bis-2-(2-ethoxy-l,3-dioxo-2,3-dihydro) phenalenyl (8). Mechanistic studies revealed that the first step of this photoreaction was a homolytic fission of the C–OC2H5 bond to 2-(2-ethoxy-1,3-dioxo-2,3-dihydro)phenalenyl radical (9) and ethoxyl radical. This homolytic fission occurred mostly from the triplet and in part from the singlet excited state of 6. Dimerization of 9 gave 8 and the disproportionation between 9 and ethoxyl radical gave acetaldehyde and 7. The photochemical behaviors of a variety of triketone derivatives were discussed.