uu.seUppsala universitets publikationer
Ändra sökning
RefereraExporteraLänk till posten
Permanent länk

Direktlänk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
1,4-Disilacyclohexa-2,5-diene: a molecular building block that allows for remarkably strong neutral cyclic cross-hyperconjugation
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Fysikalisk-organisk kemi.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.
Visa övriga samt affilieringar
2014 (Engelska)Ingår i: Chemical Science, ISSN 2041-6520, Vol. 5, nr 1, s. 360-371Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

2,3,5,6-Tetraethyl-1,4-disilacyclohexa-2,5-dienes with either four chloro (1a), methyl (1b), or trimethylsilyl (TMS) (1c) substituents at the two silicon atoms were examined in an effort to design rigid compounds with strong neutral cross-hyperconjugation between pi- and sigma-bonded molecular segments arranged into a cycle. Remarkable variations in the lowest electronic excitation energies, lowest ionization energies, and the first oxidation potentials were observed upon change of substituents, as determined by gas phase ultraviolet (UV) absorption spectroscopy, ultraviolet photoelectron spectroscopy (UPS), and cyclic voltammetry. A particularly strong neutral cyclic cross-hyperconjugation was observed in 1c. Its lowest electron binding energy (7.1 eV) is distinctly different from that of 1b (8.5 eV). Molecular orbital analysis reveals a stronger interaction between filled pi(C=C) and pi(SiR2) group orbitals in 1c than in 1a and 1b. The energy shift in the highest occupied molecular orbital is also reflected in the first oxidation potentials as observed in the cyclic voltammograms of the respective compounds (1.47, 0.88, and 0.46 V for 1a, 1b and 1c, respectively). Furthermore, 1,4-disilacyclohexadiene 1c absorbs strongly at 273 nm (4.55 eV), whereas 1a and 1b have no symmetry allowed excitations above 215 nm (below 5.77 eV). Thus, suitably substituted 1,4-disilacyclohexa-2,5-dienes could represent novel building blocks for the design of larger cross-hyperconjugated molecules as alternatives to traditional purely cross-p-conjugated analogues, and could allow for design of molecules with properties that are not accessible to those that are exclusively pi-conjugated.

Ort, förlag, år, upplaga, sidor
2014. Vol. 5, nr 1, s. 360-371
Nationell ämneskategori
Naturvetenskap
Identifikatorer
URN: urn:nbn:se:uu:diva-213891DOI: 10.1039/c3sc52389fISI: 000327601600045OAI: oai:DiVA.org:uu-213891DiVA, id: diva2:683788
Tillgänglig från: 2014-01-06 Skapad: 2014-01-05 Senast uppdaterad: 2016-03-08Bibliografiskt granskad
Ingår i avhandling
1. Conjugation in Organic Group 14 Element Compounds: Design, Synthesis and Experimental Evaluation
Öppna denna publikation i ny flik eller fönster >>Conjugation in Organic Group 14 Element Compounds: Design, Synthesis and Experimental Evaluation
2014 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

This thesis focuses on the chemical concept of conjugation, i.e., electron delocalization, and the effect it has on electronic and optical properties of molecules. The emphasis is on electron delocalization across a saturated σ-bonded segment, and in our studies these segments are either inserted between π-conjugated moieties or joined together to form longer chains. The electronic and optical properties of these compounds are probed and compared to those of traditionally π-conjugated compounds. The investigations utilize a combination of qualitative chemical bonding theories, quantum chemical calculations, chemical syntheses and different spectroscopic methods.

Herein, it is revealed that a saturated σ-bonded segment inserted between two π-systems can have optical and electronic properties similar to a cross-conjugated compound when substituents with heavy Group 14 elements (Si, Ge or Sn) are attached to the central atom. We coined the terminology cross-hyperconjugation for this interaction, and have shown it by both computational and spectroscopic means. This similarity is also found in cyclic compounds, for example in the 1,4-disilacyclohexa-2,5-dienes, as we reveal that there is a cyclic aspect of cross-hyperconjugation. Cross-hyperconjugation can further also be found in smaller rings such as siloles and cyclopentadienes, and we show on the similarities between these and their cross-π-conjugated analogues, the fulvenes. Here, this concept is combined with that of excited state aromaticity and the electronic properties of these systems are rationalized in terms of “aromatic chameleon” effects. We show that the optical properties of these systems can be rationally tuned and predicted through the choice of substituents and knowledge about the aromaticity rules in both ground and excited states.

We computationally examine the relation between conjugation and conductance and reveal that oligomers of 1,4-disilacyclohexa-2,5-dienes and related analogues can display molecular cord properties. The conductance through several σ-conjugated silicon compounds were also examined and show that mixed silicon and carbon bicyclo[2.2.2]octane compounds do not provide significant benefits over the open-chain oligosilanes. However, cyclohexasilanes, a synthetic precursor to the bicyclic compounds, displayed conformer-dependent electronic structure variations that were not seen for cyclohexanes. This allowed for computational design of a mechanically activated conductance switch.

Ort, förlag, år, upplaga, sidor
Uppsala: Acta Universitatis Upsaliensis, 2014. s. 70
Serie
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1140
Nyckelord
conjugation, conductance, electronic structure, Group 14 elements, hyperconjugation, molecular electronics, organosilicon chemistry
Nationell ämneskategori
Organisk kemi Fysikalisk kemi
Forskningsämne
Kemi med inriktning mot organisk kemi
Identifikatorer
urn:nbn:se:uu:diva-221683 (URN)978-91-554-8929-8 (ISBN)
Disputation
2014-05-27, B42, BMC, Husargatan 3, Uppsala, 13:15 (Engelska)
Opponent
Handledare
Tillgänglig från: 2014-05-06 Skapad: 2014-04-03 Senast uppdaterad: 2014-06-30

Open Access i DiVA

fulltext(2094 kB)381 nedladdningar
Filinformation
Filnamn FULLTEXT01.pdfFilstorlek 2094 kBChecksumma SHA-512
afd1a8f10ed5b090bfbd49b7776845aa12f5ff8cf947b6af287c9f4603a6b0d697884e84b563912c2b22f333547afdaae68581791d47a0b29103496974bcfb34
Typ fulltextMimetyp application/pdf

Övriga länkar

Förlagets fulltext

Personposter BETA

Emanuelsson, RikardHeijkenskjöld, FilipNauroozi, DjawedKarlsson, LeifFeifel, RaimundPettersson, RolandOtt, SaschaOttosson, Henrik

Sök vidare i DiVA

Av författaren/redaktören
Emanuelsson, RikardHeijkenskjöld, FilipNauroozi, DjawedKarlsson, LeifFeifel, RaimundPettersson, RolandOtt, SaschaOttosson, Henrik
Av organisationen
Institutionen för kemi - BMCFysikalisk-organisk kemiMolekyl- och kondenserade materiens fysikMolekylär biomimetikAnalytisk kemiSyntetisk organisk kemi
Naturvetenskap

Sök vidare utanför DiVA

GoogleGoogle Scholar
Totalt: 381 nedladdningar
Antalet nedladdningar är summan av nedladdningar för alla fulltexter. Det kan inkludera t.ex tidigare versioner som nu inte längre är tillgängliga.

doi
urn-nbn

Altmetricpoäng

doi
urn-nbn
Totalt: 1220 träffar
RefereraExporteraLänk till posten
Permanent länk

Direktlänk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf