title: Configuration- and conformation-dependent electronic-structure variations in 1,4-disubstituted cyclohexanes enabled by a carbon-to-silicon exchange.
abstract: Cyclohexane, with its well-defined conformers, could be an ideal force-controlled molecular switch if it were to display substantial differences in electronic and optical properties between its conformers. We utilize σ conjugation in heavier analogues of cyclohexanes (i.e. cyclohexasilanes) and show that 1,4-disubstituted cyclohexasilanes display configuration- and conformation-dependent variations in these properties. Cis- and trans-1,4-bis(trimethylsilylethynyl)cyclohexasilanes display a 0.11 V difference in their oxidation potentials (computed 0.11 V) and a 0.34 eV difference in their lowest UV absorption (computed difference between first excitations 0.07 eV). This is in stark contrast to differences in the corresponding properties of analogous all-carbon cyclohexanes (computed 0.02 V and 0.03 eV, respectively). Moreover, the two chair conformers of the cyclohexasilane trans isomer display large differences in electronic-structure-related properties. This enables computational design of a mechanically force-controlled conductance switch with a calculated single-molecule ON/OFF ratio of 213 at zero-bias voltage.
authors.affiliation: Department of Chemistry - BMC, Uppsala University, Box 576, 751 23 Uppsala (Sweden).
authors.forename: Rikard
authors.initials: R
authors.lastname: Emanuelsson
authors.forename: Henrik
authors.initials: H
authors.lastname: Löfås
authors.forename: Andreas
authors.initials: A
authors.lastname: Wallner
authors.forename: Djawed
authors.initials: D
authors.lastname: Nauroozi
authors.forename: Judith
authors.initials: J
authors.lastname: Baumgartner
authors.forename: Christoph
authors.initials: C
authors.lastname: Marschner
authors.forename: Rajeev
authors.initials: R
authors.lastname: Ahuja
authors.forename: Sascha
authors.initials: S
authors.lastname: Ott
authors.forename: Anton
authors.initials: A
authors.lastname: Grigoriev
authors.forename: Henrik
authors.initials: H
authors.lastname: Ottosson
keywords: conformational analysis; conjugation; electronic structure; molecular switches; silanes