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.

Properties and applications of polysilanes

“…Emanuelsson et al . studied the relationship between conformational effects and conductance of 1,4‐disubstituted cyclohexasilanes anchored with thiophenyl groups (Figure ) . Conductance measurements using the aforementioned STM‐break junction technique revealed that the trans‐ conformer with both the substituents in equatorial positions (Figure , right) was more conducting than the trans‐ conformer with both the substituents in axial positions (Figure , left).…”

The Correlation of Electrochemical Measurements and Molecular Junction Conductance Simulations in β‐Strand Peptides

“…The shift in the formal potential of 480 mV is significantly higherc ompared with other conformation-dependents tructures such as cis-trans cyclohexasilanes (110 mV). [21] This vast formal potentiald rop in our peptides provides two distinct states (i.e.,o n/off)w ith as izeable differential, which is ideal for the design of molecular switches. Defining the electron transfer pathway in peptides attached to am onolayer (electrode) is crucial to the design of singlemolecule junction devices.…”

Cardiac Glycoside Constituents of Streblus asper with Potential Antineoplastic Activity

“…This probably resulted from the impact of the c/d-ring conformational change upon formation of the C-14/C-15 double bond, as evidenced previously. 34 When evaluated toward the HT-29 cell line, 30 5b and 5d were cytotoxic, but 5c, 5e , and 5f were all inactive in this regard (Table 5). …”