Regularly Tuning Quantum Interference in Single‐Molecule Junctions through Systematic Substitution of Side Groups with Varied Electron Effects^†

Abstract

Comprehensive SummaryInvestigating the quantum interference effect in single molecules is essential to comprehensively understand the underlying mechanism of single‐molecule charge transport. In this study, we employed the mother molecule m‐OPE and introduced a series of side groups with various electronic effects at the 2‐position of the central phenyl ring, creating four daughter m‐OPE derivatives. The single molecular conductivities of these molecule wires were measured using the scanning tunneling microscope breaking junction technique. Our findings demonstrate that the substitutions regularly modulate the destructive quantum interference occurring within the m‐OPE molecules. By combining optical and electrochemical investigations, along with density functional theory computations, we discover that the conductivity of the molecules corresponds to the electron‐donating/withdrawing ability of the substituents. Specifically, by adjusting the electron structures of the molecular backbone, we can systematically tailor the destructive quantum interference in the m‐OPE molecules.

Effects of Connectivity Isomerization on Electron Transport Through Thiophene Heterocyclic Molecular Junction

“…Among them, it is extremely interesting to find that the same aromatic molecular cores with different substitution positions of anchoring groups (connectivity isomerization) ,,− profoundly affect the electron transport pathway and single-molecule conductance. A typical example is that the conductance value of meta -substituted benzene molecular junctions is significantly lower than that of ortho- and para- substituted counters, ,,,, which arise from the destructive quantum interference (DQI) effect caused by the different lengths of the electron transmission paths of the central benzene ring. Thus, the chemical diversity of oligo­(arylene ethynylene) (OAEs) has been widely explored to clarify the impact of the connectivity isomerization of an aromatic unit on their electronic properties in molecular junctions.…”