| Sumario: | The conductance and the decay of conductance as a function of molecular length within a homologous series of oligoynes, MeSi - (C≡C) - SiMe (n = 2, 3, 4, or 5), is shown to depend strongly on the solvent medium. Single molecule junction conductance measurements have been made with the I(s) method for each member of the series MeSi - (C≡C) - SiMe (n = 2, 3, 4, and 5) in mesitylene (MES), 1,2,4-trichlorobenzene (TCB), and propylene carbonate (PC). In mesitylene, a lower conductance is obtained across the whole series with a higher length decay (β ≈ 1 nm). In contrast, measurements in 1,2,4-trichlorobenzene and propylene carbonate give higher conductance values with lower length decay (β ≈ 0.1 and 0.5 nm respectively). This behavior is rationalized through theoretical and computational investigations, where β values are found to be higher when the contact Fermi energies are close to the middle of the HOMO-LUMO gap but decrease as the Fermi energies approach resonance with either the occupied or unoccupied frontier orbitals. The different conductance and β values between MES, PC, and TCB have been further explored using DFT-based models of the molecular junction, which include solvent molecules interacting with the oligoyne backbone. Good agreement between the experimental results and these >solvated> junction models is achieved, giving new insights into how solvent can influence charge transport in oligoyne-based single molecule junctions.
|
|---|
