Pulse radiolysis study of dimer cation formation of aromatic hydrocarbons in benzonitrile solution

Kira, Akira; Arai, Shigeyoshi; Imamura, Masashi

doi:10.1021/j100652a005

Cited by 69 publications

(32 citation statements)

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“…In this case only the basic form of the semithionine THO is formed, which does not absorb at 780 nm.7 Hence the absorption observed is due to the DMA cation radical only. From its absorption at 780 nm it can be concluded that, according to the optical density spectrum given in ref 20, the absorption at 600 nm is also negligible relative to the thionine ground state absorption. The spectra were taken with dye concentrations of 2 X 6 X lo", 4 X lo", and 5 X lo-' M, respectively.…”

Section: The Intermediates Of Thionine Photoreductions Have Been Extementioning

confidence: 93%

Investigation of physical triplet quenching by electron donors

Steiner¹,

Winter²,

Kramer³

1977

J. Phys. Chem.

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Absolute radical yields, as determined by flash spectroscopy, are reported for the reaction of the thionine triplet 3TH+ and its protonated form 3TH22+ with a variety of electron donors in methanolic solution. The yields are extrapolated to infinite donor concentrations. Two methods of obtaining absolute yields are described. The different yields with different donors are due to partial physical quenching of the triplets in the electron transfer reaction. The results are discussed in terms of different models, capable of explaining bimolecular intersystem crossing processes. A triplet exciplex as an intermediate in the electron transfer reaction is favored.

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Section: The Intermediates Of Thionine Photoreductions Have Been Extementioning

confidence: 93%

Investigation of physical triplet quenching by electron donors

Steiner¹,

Winter²,

Kramer³

1977

J. Phys. Chem.

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“…In the vast majority of aromatic compounds, the observed reaction is removal of a n electron followed by association of the radical cation produced with neutral molecules to give aggregates ((Mes),' in the scheme). Examples of such charged aggregates are known for most types of polynuclear aromatics and their formation is well documented for the vapour phase [17], in solution [lS, 17,19,27], and in crystalline solids [14,16]. The argument for formation of such aggregates in the columnar phase of discotic triphenylene derivatives is further supported by the observation that both triphenylene (see figure 2) and hexamethoxytriphenylene [28] form charged dimers and that such charge delocalized species are favoured in cyclophanes [29] which share the stacked aromatic ring motif found in the columnar phase.…”

Section: The Oxidation Of 23671011-hexahexylthiotriphenylenementioning

confidence: 99%

“…A strong (but not yet compelling) case can, therefore, be made that the localized states in the conducting mesophase are (Mes)"', polaron-like, structures in which the charge is spread over several molecules and this possibility is being further investigated. The formation and stabilization of polarons is associated with a local distortion of the lattice structure and in this particular case it is likely that there would be local ordering of the relative orientation of neighbouring aromatic rings (see figure 2) so as to maximize intermolecular interactions [27]. For mesogens such as HTT6, where steric effects result in a strong preference for a spiral structure [30], stabilization of this type would be inhibited.…”

Section: The Oxidation Of 23671011-hexahexylthiotriphenylenementioning

confidence: 99%

ESR studies of radical cations produced on doping discotic liquid crystals with Lewis acids

et al. 1992

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We have shown previously that doping the D,, phase of 2,3,6,7,10,11-hexahexyloxytriphenylene (HAT6) with 1-5 mole per cent of a Lewis acid converts it from an insulator to a p-type semiconductor. Herein, ESR spectroscopic studies establish that this and related oxidation reactions produce radical cations, but that these radical cations can be of several types. For instance, oxidation of the parent hydrocarbon triphenylene (TP) with aluminium trichloride in carbon disulphide solution gives a non-covalently bonded dimer (TP);' in which the charge is delocalized over two aromatic nuclei. Oxidation of HAT6 in solution gives either charged aggregates (HAT6),+ or the monomeric radical cation (HAT6) +. Formation of (TP):, (HAT6);, or (HAT6).+ involves removal of an electron from a norbital. An alternative reaction is revealed by studies of 2,3,6,7,10,1 l-hexahexylthiotriphenylene (HTT6): removal of an electron from a a-orbital. In this case a cation with a novel two-centre, three-electron, sulphur-sulphur bond is formed. Electronic conduction in doped neat HAT6 involves a mechanism in which the charge carrier hops between localized states. These localized states may be discrete (HAT6) + ions but are more probably (HAT6);' aggregates or polarons.

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“…Kira et al (14) have recorded the transient spectrum of the monomer cation of 1,2-benzanthracene in benzonitrile solution in the region 11-14 kK which has a very strong band at 11.3 kK. This is very close to the band observed at 11.1 kK in the boric acid glass.…”

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confidence: 77%