title: Intramolecular charge resonance in dimer radical anions of di-, tri-, tetra-, and pentaphenylalkanes.
abstract: Intramolecular dimer radical anions of di-, tri-, tetra-, and pentaphenylalkanes were investigated on the basis of absorption spectral measurements during γ-radiolysis in 2-methyltetrahydrofuran (MTHF) glassy matrix at 77 K and theoretical calculations. The absorption spectrum of 1,1,2,2-tetraphenylethane (1,1,2,2-Ph(4)E) radical anion showed two bands in the near-infrared (NIR) region (900-2600 nm). One band observed at shorter wavelength than 2000 nm is assigned to the intramolecular charge resonance (CR) band between two phenyl groups of the 1,1-diphenylmethyl chromophore (1,1-dimer radical anion). The intramolecular CR band of the 1,1-dimer radical anion was observed for various alkanes having 1,1-diphenylmethyl chromophore such as 1,1,1-triphenylmethane (1,1,1-Ph(3)M), 1,1,1,1-tetraphenylmethane (1,1,1,1-Ph(4)M), and so on. The other intramolecular CR band observed at longer wavelength than 2200 nm is assigned to intramolecular dimer radical anion between two phenyl groups of the 1,2-diphenylethyl chromophore (1,2-dimer radical anion). The intramolecular CR band of the 1,2-dimer radical anion was observed for various alkanes having a 1,2-diphenylethyl chromophore, such as 1,1,2-triphenylethane (1,1,2-Ph(3)E), 1,1,2,2-Ph(4)E, and 1,1,1,2,2-pentaphenylethane (1,1,1,2,2-Ph(5)E) and so on. No dimer radical anion was observed for 1,n-diphenylalkanes (n > 2) without 1,1-diphenylmethyl chromophore. The relationship between the structure and negative charge delocalization over two phenyl groups connected by an sp(3) carbon is discussed.
authors.affiliation: The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan.
authors.forename: Sachiko
authors.initials: S
authors.lastname: Tojo
authors.forename: Mamoru
authors.initials: M
authors.lastname: Fujitsuka
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Majima
mesh_terms: D000473:Alkanes / Q000737:chemistry*; D000838:Anions / Q000737:chemistry*; D019281:Dimerization; D004583:Electrons; D005609:Free Radicals / Q000737:chemistry*; D008697:Methane / Q000031:analogs & derivatives* / Q000737:chemistry; D015394:Molecular Structure; D013730:Terphenyl Compounds / Q000737:chemistry*
chemical_list: D000473:Alkanes; D000838:Anions; D005609:Free Radicals; D013730:Terphenyl Compounds; C517711:tetraphenylmethane; D008697:Methane