From Solution to Surface: Persistence of the Diradical Character of a Diindenoanthracene Derivative on a Metallic Substrate

TL;DR

This study demonstrates that the diradical character of a diindenoanthracene derivative can persist on a metallic surface, which is promising for integrating radical-based materials into electronic devices.

Contribution

It shows that the diradical character of a protected diindenoanthracene derivative remains on a metallic substrate, supported by experimental and theoretical evidence.

Findings

Detection of singlet-triplet excitations on single molecules

Molecular geometry influences radical site delocalization

Diradical character persists on metallic surfaces

Abstract

Organic diradicals are envisioned as elementary building blocks for designing a new generation of spintronic devices and have been used in constructing prototypical field effect transistors and non-linear optical devices. Open-shell systems, however, are also reactive, thus requiring design strategies to protect their radical character from the environment, especially when they are embedded into solid-state devices. Here, we report the persistence on a metallic surface of the diradical character of a diindeno[b,i]anthracene (DIAn) core protected by bulky end-groups. Our scanning tunneling spectroscopy measurements on single-molecules detected singlet-triplet excitations that were absent for DIAn species packed in assembled structures. Density functional theory simulations unravel that molecular geometry on the metal substrate can crucially modify the value of the single-triplet gap via the delocalization of the radical sites. The persistence of the diradical character over metallic substrates is a promising finding for integrating radical-based materials in functional devices.