Substitution Pattern Controlled Quantum Interference in [2.2]Paracyclophane-Based Single-Molecule Junctions
Ksenia Reznikova (University of Basel)
C. Hsu (Kavli institute of nanoscience Delft, TU Delft - QN/van der Zant Lab)
Werner M. Schosser (Universität Augsburg)
Almudena Gallego (University of Basel)
Katawoura Beltako (Universität Augsburg)
Fabian Pauly (Universität Augsburg)
H.S.J. van der Zant (Kavli institute of nanoscience Delft, TU Delft - QN/van der Zant Lab)
Marcel Mayor (Karlsruhe Institut für Technologie, University of Basel, Sun Yat-sen University)
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Abstract
Quantum interference (QI) of electron waves passing through a single-molecule junction provides a powerful means to influence its electrical properties. Here, we investigate the correlation between substitution pattern, conductance, and mechanosensitivity in [2.2]paracyclophane (PCP)-based molecular wires in a mechanically controlled break junction experiment. The effect of the meta versus para connectivity in both the central PCP core and the phenyl ring connecting the terminal anchoring group is studied. We find that the meta-phenyl-anchored PCP yields such low conductance levels that molecular features cannot be resolved; in the case of para-phenyl-coupled anchoring, however, large variations in conductance values for modulations of the electrode separation occur for the pseudo-para-coupled PCP core, while this mechanosensitivity is absent for the pseudo-meta-PCP core. The experimental findings are interpreted in terms of QI effects between molecular frontier orbitals by theoretical calculations based on density functional theory and the Landauer formalism.