Molecular structure elucidation with charge-state control

TL;DR

This study demonstrates control over molecular charge states on insulating surfaces, enabling atomic-resolution imaging of structural and electronic changes in molecules across different charge states, with implications for molecular electronics and catalysis.

Contribution

It introduces a method to control and image molecular charge states at atomic resolution using atomic force microscopy with CO tips on insulating films, revealing charge-dependent structural and electronic properties.

Findings

Charge state influences molecular conformation and bond order.

Atomic resolution imaging of molecules in multiple charge states.

Charge-dependent changes in aromaticity and conjugation in macrocycles.

Abstract

The charge state of a molecule governs its physicochemical properties, such as conformation, reactivity and aromaticity, with implications for on-surface synthesis, catalysis, photo conversion and applications in molecular electronics. On insulating, multilayer NaCl films we control the charge state of organic molecules and resolve their structures in neutral, cationic, anionic and dianionic states by atomic force microscopy, obtaining atomic resolution and bond-order discrimination using CO functionalized tips. We detect changes in conformation, adsorption geometry and bond-order relations for azobenzene, tetracyanoquinodimethane and pentacene in multiple charge states. Moreover, for porphine we investigate the charge-state-dependent change of aromaticity and conjugation pathway in the macrocycle. This work opens the way to studying chemical-structural changes of individual molecules for a wide range of charge states.