Photolysis of cyclotetrasilanes. Remarkable dependence on molecular structure

Shizuka, Haruo; Murata, Kazuyuki; Arai, Yasushi; Tonokura, Kenichi; Tanaka, Hideaki; Matsumoto, Hideyuki; Nagai, Yoichiro; Gillette, Greg; West, Robert

doi:10.1039/f19898502369

Cited by 17 publications

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“…2 and table 1. This trend can be understood by considering the fact that the reactivity for the photolysis of the former (planar form) is greater than that of the latter (bent form) even at 77 K. 31 That is, the Si-Si bond length(s) for the former may become long in the S: state compared to that of the latter.…”

Section: Av = a E * + A Ementioning

confidence: 99%

Fluorescence of cyclotetrasilanes in rigid glass at 77 K, a remarkably large Stokes shift

Shizuka¹,

Murata²,

Arai³

et al. 1989

J. Chem. Soc., Faraday Trans. 1

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The fluorescence of cyclotetrasilanes with an extremely large Stokes shift (up to 13700 cm-l) has been observed in rigid matrices at 77 K. The large Stokes shift is interpreted in terms of variation in potential energy for the S, and So states as a function of the ring Si-Si bond distance. Fluorescence properties are dependent on the molecular structures (planar and bent forms) of the compounds ; the fluorescence quantum yield, lifetime, and Stokes shift for the former are greater than those for the latter.

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Section: Av = a E * + A Ementioning

confidence: 99%

Fluorescence of cyclotetrasilanes in rigid glass at 77 K, a remarkably large Stokes shift

Shizuka¹,

Murata²,

Arai³

et al. 1989

J. Chem. Soc., Faraday Trans. 1

Self Cite

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“…The photochemistry of cyclic oligosilanes has been studied extensively because these compounds are important sources for reactive intermediates such as silyl radicals, silylenes, and disilenes [1][2][3][4][5][6][7]. However, there are few reports on the photochemistry of the corresponding cyclic oligogermanes.…”

Section: Introductionmentioning

confidence: 99%

Re-examination of the photochemical reaction of octaisopropylcyclotetragermane

Wakasa

Takamori

Takayanagi

et al. 2007

Journal of Organometallic Chemistry

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Peralkylated Four- and Five-Membered Cyclosilanes Containing a Heteroatom: Synthesis, Structure, and Properties

Watanabe

Suzuki

Takahashi

et al. 2002

Eur. J. Inorg. Chem.

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Seventeen peralkylated four-and five-membered heteroatom-containing silacycles [R 1 R 2 Si] n X [R 1 = iPr and/or R 2 = tBuCH 2 ; n = 3; X = CH 2 (1a, 1b), NR 3 (R 3 = C 6 H 11 ) (3a−d), O (5a−c), and n = 4; X = CH 2 (2a, 2b), NR 3 (R 3 = C 6 H 11 or Pr) (4a−d), and O (6a, 6b)] have been synthesized and characterized. The structural features of twelve compounds − 1b, 3a−d, and 5b (Si 3 X) and 2a, 4a−c, 6a, and 6b (Si 4 X) − determined by X-ray analysis have been investigated and geometrical differences between the silacycles bearing neopentyl groups and those with isopropyl groups as bulky substituents on silicon atoms have been identified. The ring strain energies for the compounds [R 2 Si] n X [n = 3, 4; R = Me, iPr; X = CH 2 , N(iPr), NMe, O, SiH 2 ], estimated by theoretical calculations at the PM3 level, are discussed in relation to experimentally ascertained structural features of the silacycles [R 2 Si] n X (n = 3, 4; R = iPr; X = CH 2 , NC 6 H 11 , O, SiR 2 ). 29 Si NMR spectra for 1−6 showed that the resonances for the α-silicon atoms attached to the heteroatoms X in the two ring-size series were shifted downfield by a deshielding effect due to an electronegative atom X; larger electronegativity (En) of X caused this effect at lower field. The chemical shifts of the Si α atoms showed a good linear correlation with the electronegativities of the heteroatoms X in the [R 2 Si] n X cycles. In the UV spectra for 1−6, little difference in [a] the longest-wavelength absorption (LWA) maxima was observed for [(iPr) 2 Si] n X and [(tBuCH 2 ) 2 Si] n X of the same ring size. The LWA bands for 1−6 and related compounds could be roughly classified into four groups: (a) [R 2 Si] 3 X (X = SiR 2 , GeRЈ 2 ) λ = 286−300 nm; (b) [R 2 Si] 3 X (X = CH 2 , NR 3 , O) (1, 3, 5), λ = 230−250 nm; (c) [R 2 Si] 4 X (X = SiR 2 , GeRЈ 2 ) λ = 274−280 nm; (d) [R 2 Si] 4 X (X = CH 2 , NR 3 , O) (2, 4, 6), λ = 250−260 nm. With the aid of the ionization potentials and the transition energies (E T ), the HOMO and LUMO levels for the series of compounds and the related ones were experimentally evaluated. The HOMO and LUMO levels thus obtained for [R 2 Si] 3 X and [R 2 Si] 4 X (R = iPr and tBuCH 2 ; X = SiR 2 , GeRЈ 2 , CH 2 , NC 6 H 11 , O) are discussed in terms of the calculated values and frontier orbitals on the basis of PM3 levels. The theoretical prediction for bond scission in the silacycles [(iPr) 2 Si] n X (n = 3, 4; X = CH 2 , NMe, O) in which the HOMOs and LUMOs have Si−Si bonding and antibonding character, respectively, was corroborated by the good agreement with experimental results from photolysis of the silacycles [R 2 Si] n X (n = 3, 4; R = iPr and tBuCH 2 ; X = CH 2 , NC 6 H 11 , O), with bond scission occurring only at the Si−Si bonds, and not at the Si−X bonds.

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Photolysis of cyclotetrasilanes. Remarkable dependence on molecular structure

Cited by 17 publications

References 0 publications

Fluorescence of cyclotetrasilanes in rigid glass at 77 K, a remarkably large Stokes shift

Fluorescence of cyclotetrasilanes in rigid glass at 77 K, a remarkably large Stokes shift

Re-examination of the photochemical reaction of octaisopropylcyclotetragermane

Peralkylated Four- and Five-Membered Cyclosilanes Containing a Heteroatom: Synthesis, Structure, and Properties

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