In Search of Flexible Molecular Wires with Near Conformer-Independent Conjugation and Conductance: A Computational Study
2014 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 11, 5637-5649 p.Article in journal (Refereed) Published
Oligomers of 1,4-disila/germa/stannacyclohexa-2,5-dienes as well as all-carbon 1,4-cyclohexadienes connected via E-E single bonds (E = C, Si, Ge, or Sn) were studied through quantum chemical calculations in an effort to identify conformationally flexible molecular wires that act as molecular "electrical cords" hang conformer-independent conjugative and conductive properties. Our oligomers display neutral hyperconjugative interactions (sigma/pi-conjugation) between adjacent sigma(E-E) and pi(C=C) bond orbitals, and these interactions do not change with conformation. The energies and spatial distributions of the highest occupied molecular orbitals of methyl-, silyl-, and trimethylsilyl (TMS)-substituted 1,4-disilacyclohexa-2,5-diene dimers, and stable conformers of trimers and tetramers, remain rather constant upon Si-Si bond rotation. Yet, steric congestion may be a concern in some of the oligomer types. The calculated conductances for the Si-containing tetramers are similar to that of a sigma-conjugated linear all-anti oligosilane (a hexadecasilane) with equally many bonds in the conjugated paths. Moreover, the Me-substituted 1,4-disilacyclohexadiene tetramer has modest conductance fluctuations with Si-Si bond rotations when the electrode-electrode distance is locked (variation by factor similar to 30), while the fluctuations under similar conditions are larger for the analogous TMS-substituted tetramer. When the electrode-electrode distance is changed several oligomers display small conductance variations within certain distance intervals, e.g., the mean conductance of TMS-substituted 1,4-disilacyclohexa-2,5-diene tetramer is almost unchanged over 9 A of electrode-electrode distances.
Place, publisher, year, edition, pages
2014. Vol. 118, no 11, 5637-5649 p.
Main-Group Thermochemistry, Density-Functional Theory, Noncovalent Interactions, Cross-Hyperconjugation, Excitation-Energies, Matrix-Isolation, Building-Block, Silicon, Gold, Approximation
IdentifiersURN: urn:nbn:se:kth:diva-144538DOI: 10.1021/jp409767rISI: 000333381300003ScopusID: 2-s2.0-84897831714OAI: oai:DiVA.org:kth-144538DiVA: diva2:714435
FunderSwedish Research CouncilCarl Tryggers foundation Swedish Energy AgencySwedish Foundation for Strategic Research
QC 201404282014-04-282014-04-242014-04-28Bibliographically approved