Stefan T. Bromley

Universitat de Barcelona

Published in Nature Communications, a collaborative theoretical study led by Prof. Stefan Bromley shows how to reversibly switch between closed-shell and open-shell states in radical-based 2D organic materials. The work was featured as an Editor’s Highlight (

Since the discovery of graphene, a number of inorganic 2D materials with a range of physical and chemical properties have been synthesized by top-down approaches. Such materials possess very high in-plane tensile strengths, which only allow for moderate strains generating modest electronic changes. In parallel, chemists have developed bottom-up synthesis approaches to produce 2D covalent organic frameworks (2D-COFs) based on linking arrays of molecular building blocks. Here the authors show that a particular family of 2D-COFs may provide an ideal basis for highly sensitive strain-control of electronic properties. Using persistent radicals as building blocks for new twodimensional covalent organic radical frameworks (2D-CORFs) promises to provide a platform for new flexible materials in which optical, magnetic and electrical properties can be reversibly controlled by modest structural strain.

In this work, the effect of uniaxial in-plane strain on a series of 2D covalent organic radical frameworks (2D-CORFs) is studied by means of density functional theory (DFT) based calculations. The results demonstrate that uniaxial in-plane tensile strains may be used to efficiently switch between antiferromagnetic multi-radical (i.e. open-shell) and diamagnetic quinoidal (i.e. closed-shell) states in a reversible manner. In addition, the authors demonstrate that the strain-induced electronic switching is robust at finite temperatures, which is a prerequisite for experimental viability, and thus technological applicability. Overall, their work shows that integrating bi-radical moieties into covalent 2D materials is a promising route to achieve macroscopic control over molecular-scale electronic states.

For furher info check out a “Behind the paper” post by Stefan Bromley at the Nature Portfolio Chemistry Community: Strain-induced radical change: a 2D perspective.