In Search of Flexible Molecular Wires with Near Conformer-Independent Conjugation and Conductance: A Computational Study

• DOI: 10.1021/jp409767r
• Publication Date: 2014-02-20T18:31:43Z
• Authors: Rikard Emanuelsson; Henrik Löfås; Jun Zhu; Rajeev Ahuja; Anton Grigoriev; Henrik Ottosson
• Keywords: Tetramer; Conformational isomerism; Oligomer

Oligomers of 1,4-disila/germa/stannacyclohexa-2,5-dienes as well 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 "electrical cords" having conformer-independent conjugative and conductive properties. Our oligomers display neutral hyperconjugative interactions (σ/π-conjugation) between adjacent σ(E—E) π(C═C) bond orbitals, these do not change with conformation. The energies spatial distributions the highest occupied orbitals methyl-, silyl-, trimethylsilyl (TMS)-substituted 1,4-disilacyclohexa-2,5-diene dimers, stable conformers trimers tetramers, remain rather constant upon Si–Si rotation. Yet, steric congestion may be a concern some oligomer types. calculated conductances for Si-containing tetramers are similar σ-conjugated linear all-anti oligosilane (a hexadecasilane) equally many conjugated paths. Moreover, Me-substituted 1,4-disilacyclohexadiene tetramer has modest conductance fluctuations rotations when electrode–electrode distance is locked (variation by factor ∼30), while under conditions larger analogous TMS-substituted tetramer. When changed several small variations within certain intervals, e.g., mean almost unchanged over 9 Å distances.