A Magic Ratio Rule for Beginners: a Chemist's Guide to Quantum Interference in Molecules

TL;DR

This paper introduces a new magic ratio rule (MRR) that helps chemists predict and control quantum interference effects in molecules, facilitating the design of molecular electronic devices based on connectivity and charge transport principles.

Contribution

The paper presents a novel magic ratio rule (MRR) that simplifies understanding and predicting quantum interference effects in molecular electronics, aiding molecular design.

Findings

MRR accurately predicts conductance ratios based on molecular connectivity.

Quantum interference effects are governed by key concepts like weak coupling and phase coherence.

The approach provides a minimal, chemically intuitive framework for designing molecules with desired electronic properties.

Abstract

This overview will give a glimpse into chemical design principles for exploiting quantum interference (QI) effects in molecular-scale devices. Direct observation of room temperature QI in single-molecule junctions has stimulated growing interest in fabrication of tailor-made molecular electronic devices. Herein, we outline a new conceptual advance in the scientific understanding and technological know-how necessary to control QI effects in single molecules by chemical modification. We start by discussing QI from a chemical viewpoint and then describe a new magic ratio rule (MRR), which captures a minimal description of connectivity-driven charge transport and provides a useful starting point for chemists to design appropriate molecules for molecular electronics with desired functions. The MRR predicts conductance ratios, which are solely determined by QI within the core of polycyclic aromatic hydrocarbons (PAHs). The manifestations of QI and related quantum circuit rules for materials discovery are direct consequences of the key concepts of weak coupling, locality, connectivity, mid-gap transport and phase coherence in single-molecule junctions.