Protonation tuning of quantum interference in azulene-type single-molecule junctions

Abstract

The protonation of azulene cores offers significant conductance tuning in single-molecule junctions with quantum interference.

Controlling destructive quantum interference in tunneling junctions comprising self-assembled monolayers via bond topology and functional groups

“… 16 Subsequent studies verified these findings in a variety of experimental platforms and a consensus emerged that, provided the destructive QI feature (anti-resonances in transmission) is sufficiently close to the Fermi level, E F , cross-conjugation leads to QI. 17 – 24 However, experimental studies on conjugation patterns other than AC / AQ are currently limited to ring substitutions such as meta -substituted phenyl rings , 25 – 32 or varied connectivities in azulene, 33 – 35 which differ fundamentally 5 , 11 , 36 – 38 from cross-conjugated bond topologies 23 , 39 , 40 because they change tunneling pathways, molecular-lengths and bond topology simultaneously (Table S1 † ). Isolating these variables is however important because the only primary observable is conductance, which varies exponentially with molecular length.…”

Two‐Terminal Molecular Memory through Reversible Switching of Quantum Interference Features in Tunneling Junctions

“…In π‐conjugated molecules, they are generally ascribed to cross‐conjugation,4, 5, 6, 7 meta ‐substitution,8,9 or particular spatial arrangements 10,11. Of particular interest are systems capable of toggling QI effects through external inputs;12, 13, 14 however, control over QI effects is currently limited to transient, single‐molecule junctions and/or comparisons of different compounds in different environments,15, 16, 17 for example, the ex operando (electro)chemical interconversion between a cross‐conjugated quinone and linearly conjugated hydroquinone 18,19. Herein we show that self‐assembled monolayers (SAMs) of a cross‐conjugated compound incorporating a tetracyanoquinodimethane (TCNQ) unit, TCNAQ (Figure 1), on different metal substrates can be switched between, and addressed in, two conductance states (ON and OFF) in a two‐terminal proto‐device using eutectic Ga–In (EGaIn) top contacts.…”

Probing Lewis acid–base interactions in single-molecule junctions

“…[1][2][3] Regulating charge transport at the single-molecule level is a key step in the development of molecular circuits. In the last decade, several methods were applied for this purpose, including electrochemical gating, [4][5][6] pH variation, [7][8][9] light irradiation, 10 chemical tuning of two distinct charge transport pathways, 11 and mechanical control of the molecular conformation or metal-molecule contact geometry 12,13 as well as the insertion of a heteroatom in the aromatic core. 14,15 Although these results provide important insights into the electronic properties of single-molecule junctions, it is highly desirable to realize molecular devices exhibiting a controllable current flow.…”