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Volumn 8, Issue , 1996, Pages 1633-1643

Photoinduced electron transfer from enol silyl ethers to quinone. Part 2. Direct observation of ion-pair dynamics by time-resolved spectroscopy

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EID: 0001426756     PISSN: 03009580     EISSN: None     Source Type: Journal    
DOI: 10.1039/p29960001633     Document Type: Article
Times cited : (33)

References (111)
  • 7
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    • note
    • For the formation of enone (E) and adduct (A) in dichloromethane and acetonitrile, see Tables 1 and 2 in Ref. 1.
  • 8
    • 54249114004 scopus 로고    scopus 로고
    • note
    • Corresponding to the full width at half maximum (fwhm) of the Gaussian bandshape.
  • 17
    • 54249164518 scopus 로고    scopus 로고
    • note
    • (a) Note that the white light continuum for the picosecond laser-flash system only extended to 400 nm. (b) On the other hand, the extended spectral range of the nanosecond time-resolved spectrometer allowed the reactive intermediates to be observed in the wavelength region from 300 to 900 nm.
  • 18
    • 0000318373 scopus 로고    scopus 로고
    • .+ (which absorbs visible light) is due to the π conjugation of the alkene cation-radical moiety with the phenyl substituent. See R. Rathore and J. K. Kochi, J. Org. Chem., 1996, 61, 627.
    • (1996) J. Org. Chem. , vol.61 , pp. 627
    • Rathore, R.1    Kochi, J.K.2
  • 19
    • 0000956893 scopus 로고
    • .+ closely resembles those of styrene cation radicals, as described by L. J. Johnston and N. P. Schepp, J. Am. Chem. Soc., 1993, 115, 6564.
    • (1993) J. Am. Chem. Soc. , vol.115 , pp. 6564
    • Johnston, L.J.1    Schepp, N.P.2
  • 20
    • 54249111840 scopus 로고    scopus 로고
    • note
    • .+ occurred simultaneously in dichloromethane on the 1 to 3 ns timescale to a weak residual absorption of the hydrochloranil radical (vide infra).
  • 24
    • 54249102608 scopus 로고    scopus 로고
    • note
    • -1, respectively, that were formed in more or less equimolar amounts according to eqn. (2). Moreover, the simultaneous growth of the 450 and 550 nm absorbances were roughly comparable (τ ∼ 0.7 ns).
  • 25
    • 54249169079 scopus 로고    scopus 로고
    • note
    • -6 M.
  • 26
    • 54249161413 scopus 로고    scopus 로고
    • note
    • Note the quenching rate constant for 2-phenycyclohexanone enol silyl ether 9 in Table 2 (entry 6) was unusually slow (vide infra).
  • 27
    • 54249097407 scopus 로고    scopus 로고
    • note
    • 1:, in eqn. (3). (See ref. 18).
  • 29
    • 54249086619 scopus 로고    scopus 로고
    • note
    • ., and it was assigned to the silyl-substituted hydrochloranil radical.
  • 35
    • 0020620983 scopus 로고
    • 1 2b (d) Furthermore, the same two bands were observed upon the photoinduced electron transfer of enol silyl ether 9 (in the presence of benzophenone and 1,2,4,5-tetracyanobenzene) by the procedure described by P. K. Das, J. Chem. Soc., Faraday Trans. 1, 1983, 79, 1135.
    • (1983) J. Chem. Soc., Faraday Trans. 1 , vol.79 , pp. 1135
    • Das, P.K.1
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    • ed. J. C. Scaiano, CRC Press, Boca Raton, FL
    • (b) C. Chatgilialoglu, in Handbook of Photochemistry, ed. J. C. Scaiano, CRC Press, Boca Raton, FL, 1989, vol II, p 1.
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    • note
    • 1
  • 39
    • 54249090703 scopus 로고    scopus 로고
    • note
    • -1) of the hydrochloranil radical.
  • 40
    • 54249143951 scopus 로고    scopus 로고
    • note
    • .+, see Figs. 1B, 3B and 6.
  • 41
    • 54249089352 scopus 로고    scopus 로고
    • note
    • 1
  • 46
    • 54249143050 scopus 로고    scopus 로고
    • note
    • RIP.
  • 47
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    • note
    • 40
  • 50
    • 54249165433 scopus 로고    scopus 로고
    • See Murov et al. in, Ref 16b p. 19
    • See Murov et al. in, Ref 16b p. 19.
  • 51
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    • Silyl enol ethers have been identified as viable electron donors by the combination of spectral, electrochemical and photoionization methods. See R. Rathore and J. K. Kochi, Tetrahedron Lett., 1994, 35, 8577.
    • (1994) Tetrahedron Lett. , vol.35 , pp. 8577
    • Rathore, R.1    Kochi, J.K.2
  • 58
    • 54249084459 scopus 로고    scopus 로고
    • note
    • 3CA* with ESE, there is usually an ambiguity as to whether H-atom transfer occurs in one or two distinct steps.
  • 61
  • 81
    • 54249107949 scopus 로고    scopus 로고
    • note
    • .- at zero salt concentration (in Fig. 8), and is very small (< 0.01).
  • 83
    • 54249122143 scopus 로고    scopus 로고
    • note
    • .+ in acetonitrile precludes a salt-effect study, and it is not possible to identify definitively the initially-formed ion pair in this solvent. It is likely that the contact radical-ion pair is first formed in both solvents, in view of the identity of the quenching processes in dichloromethane and acetonitrile.
  • 84
    • 54249124495 scopus 로고    scopus 로고
    • See Table 4 in Ref. 1
    • See Table 4 in Ref. 1.
  • 85
    • 54249159171 scopus 로고    scopus 로고
    • note
    • This exchange occurs at high (ca. 0.1 M) salt concentrations (normal salt effect) and should be distinguished from the interception of solvent-separated ion pairs (special salt effect) discussed earlier.
  • 86
    • 54249091148 scopus 로고    scopus 로고
    • note
    • + from the cation to the anion.
  • 102
    • 0001748542 scopus 로고
    • eds. M. A. Fox and M. Chanon, Elsevier, New York
    • (a) M. R. Wasielewski, in Photoinduced Electron Transfer, eds. M. A. Fox and M. Chanon, Elsevier, New York, 1988 p. 161;
    • (1988) Photoinduced Electron Transfer , pp. 161
    • Wasielewski, M.R.1
  • 105
    • 54249107223 scopus 로고    scopus 로고
    • note
    • .+] solvent-separated ion pair.
  • 106
    • 54249136290 scopus 로고
    • 2], are oxidized to cation radicals which are completely distonic. These species have 90° dihedral angles around the 'double bonds'. See S. Fukuzumi, M. Fujita, J. Otera and Y. Fujita, J. Am. Chem. Soc., 1992, 114, 10241.
    • (1992) J. Am. Chem. Soc. , vol.114 , pp. 10241
    • Fukuzumi, S.1    Fujita, M.2    Otera, J.3    Fujita, Y.4
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    • note
    • 77


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.