# Probing Ultrastrong Through‐Space Electronic Coupling in Donor‐Acceptor Systems at the Single‐Molecule Level

## TL;DR

Researchers studied charge transport in donor-acceptor systems at the single-molecule level and found that through-space coupling can be as effective as traditional through-bond methods.

## Contribution

The study demonstrates ultrastrong through-space electronic coupling in donor-acceptor systems comparable to through-bond molecular wires.

## Key findings

- Optimized spatial proximity and electronic complementarity in D–A systems yield conductance values up to ∼0.19 G0.
- Flicker noise analysis and mechanical stretching confirm robust electronic and mechanical coupling.
- Through-space transmission is identified as the dominant charge transport mechanism.

## Abstract

Through‐space donor‐acceptor (TSDA) interactions have recently emerged as a new paradigm for charge transfer and transport in organic semiconductors. However, the intrinsic D–A coupling strength and charge transport properties at the molecular level remain unexplored in comparison to established through‐bond channels. Here, we employ a variety of single‐molecule techniques to directly probe TSDA charge transport characteristics in a series of strategically designed face‐to‐face D–A systems, revealing that optimized spatial proximity and electronic complementarity yield conductance values up to ∼0.19 G0, comparable to the best‐performing through‐bond molecular wires. Flicker noise analysis, current‐voltage characterization, and mechanical stretching measurements confirm robust electronic and mechanical coupling, while theoretical calculations and photophysical studies identify through‐space transmission as the prevailing mechanism. These findings establish non‐covalent TSDA coupling as an efficient charge‐transport channel and provide new molecular‐level insight for the design of D–A systems in organic electronics and optoelectronics.

A series of through‐space coupled donor‐acceptor (D–A) molecules is sandwiched between two electrodes to determine their single‐molecule conductance. As the D–A interaction weakens, single‐molecule conductance reduces while Flicker Noise PSD n‐value increases (coupling strength decreases). Especially for TS1, the conductance reaches 0.19 G0, and its ultra‐strong electronic coupling behaves like through‐bond interactions. Such results are entirely novel in single‐molecule electronics.