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Morisawa Y, Higaki Y, Ozaki Y. Far-Ultraviolet Spectroscopy and Quantum Chemical Calculation Studies of the Conformational Dependence on the Electronic Structure and Transitions of Cyclohexane, Methyl and Dimethyl Cyclohexane, and Decalin; Effects of Axial Substitutions on the Electronic Transitions. J Phys Chem A 2021; 125:8205-8214. [PMID: 34505772 DOI: 10.1021/acs.jpca.1c05688] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Far-ultraviolet (FUV) spectra were measured for cyclohexane, methyl cyclohexane, six isomers of dimethyl cyclohexane, and cis- and trans-decalin. Attenuated total reflection-FUV (ATR-FUV) spectroscopy, which we originally proposed, provides systematic information about the excitation states of saturated organic molecules and the hyperconjugation of σ bonds. The FUV spectra of cyclohexane and methyl cyclohexane in neat liquids showed a band with central wavelengths near 155 and 162 nm. The simulation spectrum of cyclohexane calculated by time-dependent density-functional theory (TD-DFT) (CAM-B3LYP/aug-cc-pVTZ) gives two bands at 146 and 152 nm owing to the transition from HOMO-2 to Rydberg 3pz (Tb) and those from HOMO and HOMO-1 to Rydberg 3px/3py (Ta), respectively. The simulation spectrum of methyl cyclohexane with the equatorial substituent has peaks at approximately the same positions as cyclohexane. The calculated molar absorption coefficient is larger than that of cyclohexane, estimating the observed FUV spectra very well. The FUV spectra of dimethyl cyclohexane with two methyl substituents at the equatorial positions (trans-1,2-, cis-1,3-, and trans-1,4-) and trans-decalin had similar features to those of cyclohexane and methylcyclohexane. The TD-DFT calculations revealed that the shoulders at the shorter- and longer-wavelength sides of the band center of dimethyl cyclohexane (with methyl substituents at equatorial positions) and trans-decalin are assigned to Tb and Ta, respectively. In the case of dimethyl cyclohexane with one methyl substituent in the axial position (cis-1,2-, trans-1,3-, and cis-1,4-) and cis-decalin, the band caused by Tb decreased compared to those of the other compounds. The decrease in intensity and the longer-wavelength shift of the Tb band for dimethyl cyclohexane (with one methyl group at the axial position) and cis-decalin revealed that the band on the longer-wavelength side was assigned to the overlap band of Ta and Tb. The reason for such a large spectral alternation for the axial substitution may be the increase in the orbital energy of HOMO-2, which has its electron density concentrated at the axial C-H bond. Regarding the effect of the hyperconjugation of C-C and C-H σ orbitals, the second perturbation energies of the interaction between Cα-Hax and Cβ-Hax were estimated for molecules by natural bond orbital (NBO) analysis. There is a correlation between the orbital energies of HOMO-2 and the changes in vicinal interaction by axial substitution.
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Affiliation(s)
- Yusuke Morisawa
- Department of Chemistry, School of Science and Engineering, Kindai University, Kowakae, Higashi-Osaka, Osaka 577-8502, Japan
| | - Yugo Higaki
- Department of Chemistry, School of Science and Engineering, Kindai University, Kowakae, Higashi-Osaka, Osaka 577-8502, Japan
| | - Yukihiro Ozaki
- School of Biological and Environmental Sciences, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan.,Toyota Physical and Chemical Research Institute, Yokomichi, Nagakute, Aichi 480-1192, Japan
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2
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Affiliation(s)
- Vipin B. Kumar
- School of Chemical SciencesUniversity of Auckland 23 Symonds Street Auckland 1010 New Zealand
| | - Erin M. Leitao
- School of Chemical SciencesUniversity of Auckland 23 Symonds Street Auckland 1010 New Zealand
- The MacDiarmid Institute for Advanced Materials and Nanotechnology Wellington New Zealand
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3
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Jovanovic M, Michl J. Effect of Conformation on Electron Localization and Delocalization in Infinite Helical Chains [X(CH 3) 2] ∞ (X = Si, Ge, Sn, and Pb). J Am Chem Soc 2019; 141:13101-13113. [PMID: 31306578 DOI: 10.1021/jacs.9b04780] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
An intuitive explanation of the effects of conformation (backbone dihedral angle) on electron delocalization in infinite saturated regular helices [(CH3)2]∞Si, [(CH3)2Ge]∞, [(CH3)2Sn]∞, and [(CH3)2Pb]∞ is offered in terms of the simple Ladder C model and confirmed by density functional theory calculations. The effective hole mass, which ranges from near zero to infinity as a function of conformation, is used as a measure of the degree of delocalization and relates to the effects of chain length extension in finite systems. The position of the Fermi level in reciprocal space has a simple counterpart in systems of finite length and is used to characterize the dominant mechanism, σ conjugation (geminal interactions) or σ hyperconjugation (vicinal interactions, through-bond coupling). Constructive or destructive interference of the two mechanisms produces three different delocalization regimes as a function of the backbone dihedral angle and analogy is drawn to polycyclic π-electron systems consisting of fused Hückel or Möbius four-membered rings.
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Affiliation(s)
- Milena Jovanovic
- Department of Chemistry , University of Colorado , Boulder , Colorado 80309-0215 , United States.,Institute of Organic Chemistry and Biochemistry , Czech Academy of Sciences , Flemingovo nám. 1 , 16610 Prague 6 , Czech Republic
| | - Josef Michl
- Department of Chemistry , University of Colorado , Boulder , Colorado 80309-0215 , United States.,Institute of Organic Chemistry and Biochemistry , Czech Academy of Sciences , Flemingovo nám. 1 , 16610 Prague 6 , Czech Republic
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4
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Jovanovic M, Antic D, Rooklin D, Bande A, Michl J. Intuitive Understanding of σ Delocalization in Loose and σ Localization in Tight Helical Conformations of an Oligosilane Chain. Chem Asian J 2017; 12:1250-1263. [DOI: 10.1002/asia.201700226] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Indexed: 11/10/2022]
Affiliation(s)
- Milena Jovanovic
- Department of Chemistry and Biochemistry University of Colorado Boulder CO 80309-0215 USA
- Institute of Organic Chemistry and Biochemistry Academy of Sciences of the Czech Republic Flemingovo nám. 2 16610 Prague 6 Czech Republic
| | - Dean Antic
- Department of Chemistry and Biochemistry University of Colorado Boulder CO 80309-0215 USA
| | - David Rooklin
- Department of Chemistry and Biochemistry University of Colorado Boulder CO 80309-0215 USA
| | - Annika Bande
- Department of Chemistry and Biochemistry University of Colorado Boulder CO 80309-0215 USA
- Institute of Methods for Material Development Helmholtz-Zentrum Berlin für Materialien und Energie GmbH Albert-Einstein-Str. 15 D-12489 Berlin Germany
| | - Josef Michl
- Department of Chemistry and Biochemistry University of Colorado Boulder CO 80309-0215 USA
- Institute of Organic Chemistry and Biochemistry Academy of Sciences of the Czech Republic Flemingovo nám. 2 16610 Prague 6 Czech Republic
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Zhou J, Folster CP, Surampudi SK, Jimenez D, Klausen RS, Bragg AE. Asymmetric charge separation and recombination in symmetrically functionalized σ–π hybrid oligosilanes. Dalton Trans 2017; 46:8716-8726. [DOI: 10.1039/c7dt00384f] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The flexibility of σ-conjugated silanes presents new opportunities for controlling charge transfer via changes in molecular conformation.
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Affiliation(s)
- Jiawang Zhou
- Department of Chemistry
- Johns Hopkins University
- Baltimore
- USA
| | | | | | - Daniel Jimenez
- Department of Chemistry
- Johns Hopkins University
- Baltimore
- USA
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6
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Kanazawa Y, Tsuji H, Ehara M, Fukuda R, Casher DL, Tamao K, Nakatsuji H, Michl J. Electronic Transitions in Conformationally Controlled Peralkylated Hexasilanes. Chemphyschem 2016; 17:3010-3022. [DOI: 10.1002/cphc.201600633] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Indexed: 11/08/2022]
Affiliation(s)
- Yuki Kanazawa
- SOKENDAI The Graduate University for Advanced Studies, Nishigonaka, Myodaiji Okazaki 444–8585 Japan
- Institute for Molecular Science and Research Center for Computational Science, Nishigonaka, Myodaiji Okazaki 444–8585 Japan
| | - Hayato Tsuji
- International Research Center for Elements Science (IRCELS) Institute for Chemical Research Kyoto University, Uji Kyoto 611-0011 Japan
- Department of Chemistry Faculty of Science Kanagawa University 2946 Tsuchiya Hiratsuka Kanagawa 259–1293 Japan
| | - Masahiro Ehara
- SOKENDAI The Graduate University for Advanced Studies, Nishigonaka, Myodaiji Okazaki 444–8585 Japan
- Institute for Molecular Science and Research Center for Computational Science, Nishigonaka, Myodaiji Okazaki 444–8585 Japan
- Elements Strategy Initiative for Catalysts and Batteries (ESICB) Kyoto University Kyoto 615–8520 Japan
| | - Ryoichi Fukuda
- Elements Strategy Initiative for Catalysts and Batteries (ESICB) Kyoto University Kyoto 615–8520 Japan
| | - Deborah L. Casher
- Department of Chemistry and Biochemistry University of Colorado at Boulder Boulder Colorado 80309-0215 USA
| | - Kohei Tamao
- International Research Center for Elements Science (IRCELS) Institute for Chemical Research Kyoto University, Uji Kyoto 611-0011 Japan
- RIKEN 2-1 Hirosawa Saitama 351-0198 Japan
| | - Hiroshi Nakatsuji
- Quantum Chemistry Research Institute Goryo Oohara 1–36, Nishikyo-ku Kyoto 615–8245 Japan
| | - Josef Michl
- Department of Chemistry and Biochemistry University of Colorado at Boulder Boulder Colorado 80309-0215 USA
- Institute of Organic Chemistry and Biochemistry Academy of Sciences of the Czech Republic Flemingovo nám. 2 16610 Prague Czech Republic
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7
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Jiang X, Terao K, Chung W, Naito M. Chain dimensions and intermolecular interactions of polysilanes bearing alkyl side groups over the UV thermochromic temperature. POLYMER 2015. [DOI: 10.1016/j.polymer.2015.05.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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8
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Tsuji H, Fogarty HA, Ehara M, Fukuda R, Casher DL, Tamao K, Nakatsuji H, Michl J. Electronic transitions in conformationally controlled tetrasilanes with a wide range of SiSiSiSi dihedral angles. Chemistry 2014; 20:9431-41. [PMID: 25043859 DOI: 10.1002/chem.201403495] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Indexed: 11/08/2022]
Abstract
Unlike π-electron chromophores, the peralkylated n-tetrasilane σ-electron chromophore resembles a chameleon in that its electronic spectrum changes dramatically as its silicon backbone is twisted almost effortlessly from the syn to the anti conformation (changing the SiSiSiSi dihedral angle ω from 0 to 180°). A combination of UV absorption, magnetic circular dichroism (MCD), and linear dichroism (LD) spectroscopy on conformationally controlled tetrasilanes 1-9, which cover fairly evenly the full range of angles ω, permitted a construction of an experimental correlation diagram for three to four lowest valence electronic states. The free chain tetrasilane n-Si4 Me10 (10), normally present as a mixture of three enantiomeric conformer pairs of widely different angles ω, has also been included in our study. The spectral trends are interpreted in terms of avoided crossings of 1B with 2B and 2A with 3A states, in agreement with SAC-CI calculations on the excited states of 1-7 and conformers of 10.
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Affiliation(s)
- Hayato Tsuji
- International Research Center for Elements Science (IRCELS), Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011 (Japan); Present address: Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku,Tokyo 113-0033 (Japan)
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9
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Bande A, Michl J. Conformational dependence of sigma-electron delocalization in linear chains: permethylated oligosilanes. Chemistry 2009; 15:8504-8517. [PMID: 19658142 DOI: 10.1002/chem.200901521] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The effects of sigma-electron delocalization on optical properties of saturated linear chains of permethylated oligosilanes are strongly conformation dependent. We analyze the origin of the conformational dependence of the energies of molecular orbitals and of electronic excitations in simple intuitively understandable terms by using a first-order approximation to the Hückel version of the "Ladder C" model. The analysis is supported by comparison with results of numerical calculations from time-dependent density functional theory, which agree well with experiment. To facilitate the comparison, a simple procedure has been developed that defines the overall and local fractional sigma and pi characters of a backbone molecular orbital and a fractional overall and local sigma sigma* and sigma pi* characters of an excited state for any conformation of a linear chain.
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Affiliation(s)
- Annika Bande
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309-0215, USA
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11
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Conformational relaxation of σ-conjugated polymer radical anion on picosecond scale. J Chem Phys 2009; 130:204907. [DOI: 10.1063/1.3139447] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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12
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Krempner C, Reinke H. An Approach to Dendritic Oligosilanes: Controlling the Conformation through Ring Formation. Organometallics 2007. [DOI: 10.1021/om060964k] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- C. Krempner
- Institut für Chemie der Universität Rostock, A.-Einstein-Strasse 3a, D-18059 Rostock, Germany
| | - H. Reinke
- Institut für Chemie der Universität Rostock, A.-Einstein-Strasse 3a, D-18059 Rostock, Germany
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13
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Jäger-Fiedler U, Köckerling M, Ludwig R, Wulf A, Krempner C. Hydroxysubstituierte Oligosilandendrimere – Kontrolle der elektronischen Eigenschaften durch Wasserstoffbrücken. Angew Chem Int Ed Engl 2006. [DOI: 10.1002/ange.200601598] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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14
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Jäger-Fiedler U, Köckerling M, Ludwig R, Wulf A, Krempner C. Hydroxy-Substituted Oligosilane Dendrimers: Controlling the Electronic Properties through Hydrogen Bonding. Angew Chem Int Ed Engl 2006; 45:6755-9. [PMID: 16977665 DOI: 10.1002/anie.200601598] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Ulrike Jäger-Fiedler
- Institut für Chemie der Universität Rostock, A.-Einstein-Strasse 3a, 18059 Rostock, Germany
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15
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Marschner C, Baumgartner J, Wallner A. Structurally and conformationally defined small methyl polysilanes. Dalton Trans 2006:5667-74. [PMID: 17146531 DOI: 10.1039/b613642g] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Possessing the property of sigma-bond electron delocalisation, polysilanes are a class of compounds with unique properties. In recent years major progress has been achieved in the theoretical understanding and the synthesis of polysilanes. Much insight into the connection between conformation and electronic properties has been gained from studies of defined small polysilane molecules. The transition from Wurtz type coupling reactions to the stepwise construction of polysilane molecules employing silyl anions as key intermediates has permitted access to defined compounds with a higher degree of structural complexity. Besides this, several methods have been developed to control the conformational properties and thus gain control over the electronic properties of polysilanes.
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Affiliation(s)
- Christoph Marschner
- Institut für Anorganische Chemie, Technische Universität Graz, Stremayrgasse 16, A-8010, Graz, Austria.
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16
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Shankar R, Joshi A. Synthesis, Characterization, and Photoluminescence Properties of Asymmetrically Substituted Functional Polysilanes Bearing Carbosilyl Side Chains, −[R(Me)Si]n− and −[R(Ph)Si]n− [R = (CH2)xSiR‘3; x = 2 or 3]. Macromolecules 2005. [DOI: 10.1021/ma047847q] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ravi Shankar
- Department of Chemistry, Indian Institute of Technology, Hauz Khas, New Delhi 110016, India
| | - Arti Joshi
- Department of Chemistry, Indian Institute of Technology, Hauz Khas, New Delhi 110016, India
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Saxena A, Fujiki M, Naito M, Okoshi K, Kwak G. Novel Molecular Weight and Solvatochromisms in Poly(methyl-3,3,3-trifluoropropylsilane) Induced by Cooperative Through-Space Si···F−C Interactions. Macromolecules 2004. [DOI: 10.1021/ma049546m] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Anubhav Saxena
- Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0101, Japan, and CREST-JST (Japan Science and Technology Corporation), 4-1-8 Hon-cho, Kawaguchi, Saitama 332-0012, Japan
| | - Michiya Fujiki
- Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0101, Japan, and CREST-JST (Japan Science and Technology Corporation), 4-1-8 Hon-cho, Kawaguchi, Saitama 332-0012, Japan
| | - Masanobu Naito
- Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0101, Japan, and CREST-JST (Japan Science and Technology Corporation), 4-1-8 Hon-cho, Kawaguchi, Saitama 332-0012, Japan
| | - Kento Okoshi
- Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0101, Japan, and CREST-JST (Japan Science and Technology Corporation), 4-1-8 Hon-cho, Kawaguchi, Saitama 332-0012, Japan
| | - Giseop Kwak
- Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0101, Japan, and CREST-JST (Japan Science and Technology Corporation), 4-1-8 Hon-cho, Kawaguchi, Saitama 332-0012, Japan
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Suzuki K, Kawakami Y, Velmurugan D, Yamane T. Stereoselective Synthesis of Optically Active Disilanes and Selective Functionalization by the Cleavage of Silicon−Naphthyl Bonds with Bromine. J Org Chem 2004; 69:5383-9. [PMID: 15287785 DOI: 10.1021/jo049398y] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Optically active disilanes with one chiral silicon center, (R)-1,2-dimethyl-1-(naphth-1-yl)-1,2,2-triphenyldisilane and (R)-1,2,2-trimethyl-2-(4-methoxynaphth-1-yl)-1-(naphth-1-yl)-1-phenyldisilane, were obtained by the reaction of (S)-methyl(naphth-1-yl)phenylchlorosilane (> 99% ee) with methyldiphenylsilyllithium or by the reaction of methyldiphenylchlorosilane with optically active (S)-methyl(naphth-1-yl)phenylsilyllithium and by the reaction of (S)-methyl(naphth-1-yl)phenylchlorosilane (> 99% ee) with dimethyl(4-methoxynaphth-1-yl)silyllithium. Under the optimized conditions, the reactions proceeded with almost complete inversion for the cholorosilanes and retention for the silyl anions. Optically active disilanes with two chiral centers, (1R,2R)-1,2-dimethyl-1,2-di(naphth-1-yl)-1,2-diphenyldisilane and (1S,2S)-1,2-di(4-methoxynaphth-1-yl)-1,2-dimethyl-1,2-diphenyldisilane, were obtained in high optical purity by the reactions of corresponding optically active halogenosilanes (Cl or F) with optically active silyllithiums. The silicon-silicon bond and the silicon-naphthyl bond of (R)-1,1,2-trimethyl-1,2-di(naphth-1-yl)-2-phenyldisilane and (1R,2R)-1,2-dimethyl-1,2-di(naphth-1-yl)-1,2-diphenyldisilane were cleaved without selectivity on bromination. The silicon-(4-methoxynaphth-1-yl) bond of (R)-1,2,2-trimethyl-2-(4-methoxynaphth-1-yl)-1-(naphth-1-yl)-1-phenyldisilane was regiospecifically cleaved, followed by the stereoselective cleavage of the remaining chiral silicon-naphthyl bond (94% inversion). Although the silicon-(4-methoxynaphth-1-yl) bonds of (1S,2S)-1,2-di(4-methoxynaphth-1-yl)-1,2-dimethyl-1,2-diphenyldisilane (> 99% ee) were regioselectively cleaved without silicon-silicon bond scission, remarkable racemization could not be avoided during the one-pot reaction.
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Affiliation(s)
- Keigo Suzuki
- Graduate School of Materials Science, Japan Advanced Institute of Science & Technology [JAIST], Asahidai 1-1, Tatsunokuchi, Ishikawa 923-1292, Japan.
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Tsuji H, Fukazawa A, Yamaguchi S, Toshimitsu A, Tamao K. all-anti-Pentasilane: Conformation Control of Oligosilanes Based on the Bis(tetramethylene)-Tethered Trisilane Unit. Organometallics 2004. [DOI: 10.1021/om049695t] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Hayato Tsuji
- International Research Center for Elements Science (IRCELS), Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Aiko Fukazawa
- International Research Center for Elements Science (IRCELS), Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Shigehiro Yamaguchi
- International Research Center for Elements Science (IRCELS), Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Akio Toshimitsu
- International Research Center for Elements Science (IRCELS), Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Kohei Tamao
- International Research Center for Elements Science (IRCELS), Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
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Mallesha H, Tsuji H, Tamao K. UV Absorption and Mass Spectra of n-Alkylsilyl End-Capped Anti,Cisoid-Alternating Oligosilanes up to Docosasilane (Si22). Organometallics 2004. [DOI: 10.1021/om034307t] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Honnaiah Mallesha
- International Research Center for Elements Science, Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Hayato Tsuji
- International Research Center for Elements Science, Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Kohei Tamao
- International Research Center for Elements Science, Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
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Tsuji H, Michl J, Tamao K. Recent experimental and theoretical aspects of the conformational dependence of UV absorption of short chain peralkylated oligosilanes. J Organomet Chem 2003. [DOI: 10.1016/s0022-328x(03)00162-1] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Winokur MJ, West R. X-ray Diffraction and Molecular Modeling Studies of Poly(di-n-alkylsilanes): The Near Planar Type Phases of Poly(di-n-butylsilane) and Poly(di-n-hexylsilane). Macromolecules 2003. [DOI: 10.1021/ma026017e] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- M. J. Winokur
- Department of Physics, University of Wisconsin, Madison, Wisconsin 53706, and Organosilicon Research Center, Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706
| | - R. West
- Department of Physics, University of Wisconsin, Madison, Wisconsin 53706, and Organosilicon Research Center, Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706
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Tsuji H, Terada M, Toshimitsu A, Tamao K. Sigmasigma* transition in anti,cisoid alternating oligosilanes: clear-cut evidence for suppression of conjugation effect by a cisoid turn. J Am Chem Soc 2003; 125:7486-7. [PMID: 12812467 DOI: 10.1021/ja034500e] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
On the basis of the UV absorption spectra of the anti,cisoid alternating oligosilanes, the first experimental clear-cut evidence was presented for the generally accepted idea that the sigma conjugation in polysilanes does not effectively extend through a tetrasilane fragment with a small dihedral angle such as a cisoid turn.
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Affiliation(s)
- Hayato Tsuji
- Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
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Rooklin DW, Schepers T, Raymond-Johansson MK, Michl J. Time-dependent density functional theory treatment of the first UV absorption band in all-transoid permethyloligosilanes SinMe2n + 2 (n = 2-8, 10). Photochem Photobiol Sci 2003; 2:511-7. [PMID: 12803073 DOI: 10.1039/b302087h] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The TD B3LYP/6-311G(d,p) method slightly overestimates the excitation energies of the first UV absorption band of the all-transoid conformers of SinMe2n + 2 (n = 2-8, 10), deduced from temperature-dependent measurements on conformer mixtures in hydrocarbon solvents, by a nearly constant amount (approximately 2000 cm-1). The TD B3LYP/6-31G(d) results are less satisfactory. The first band is calculated to be due to a sigma pi * excitation in Si2Me6 and to a superposition of overlapping sigma sigma * and sigma pi * excitations in the longer oligosilanes. The sigma pi * excitation is calculated to lie a little below the sigma sigma * excitation up to Si4Me10, the two transitions are nearly degenerate in Si5Me12, and the sigma sigma * excitation drops increasingly below the sigma pi * as the chain length is extended. The dipole strength of the sigma sigma * excitation grows by 4.8 D2 (D = debye) per added SiSi bond (more slowly up to n = 5) and the calculation overestimates it by a factor of about three. The sigma pi * excitation is computed to carry no or almost no oscillator strength, but as noted earlier by others, its presence is critical for the interpretation of the observed thermochromism. Upon cooling below room temperature, the first absorption maximum is blue-shifted in short chains and red-shifted in long chains. Unlike the prior investigators, we attribute the blue shift to the disappearance of hot bands built on the sigma pi * origin using intensity borrowing sigma-pi mixing vibrations (b1 in Si3Me8). As usual, the red shift is attributed to the disappearance of twisted conformers, which have higher calculated sigma sigma * excitation energies.
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Affiliation(s)
- David W Rooklin
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309-0215, USA
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Sanji T, Takase K, Sakurai H. Helical-sense programming through polysilane-poly(triphenylmethyl methacrylate) block copolymers. J Am Chem Soc 2001; 123:12690-1. [PMID: 11741439 DOI: 10.1021/ja0167250] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- T Sanji
- Department of Pure and Applied Chemistry, Science University of Tokyo, Chiba 278-8510, Japan
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