Rational Design of Electric Field-Responsive Building Blocks for All-Organic 2D Magnetoelectric Materials
Kílian Jutglar-Lozano, Mercè Deumal, Jordi Ribas‐Ariño, Stefan T. Bromley
Abstract
High Resolution Image Download MS PowerPoint Slide Development of technologically promising magnetoelectric materials, where magnetic properties can be controlled by electric fields (E-fields), has focused on inorganic systems. Here, we propose a strategy for modulating magnetic exchange coupling ( J ) in purely organic systems through experimentally realizable E-fields. Our approach leverages two established concepts: (i) E-field-induced twisting of dipolar organic linkers and (ii) control of J via conformational changes in organic diradicals. Using density functional theory calculations, we investigated the effects of applied E-fields on diradicals with two coplanar spin-carrying trioxotriangulene (TOT) radicals connected by dipolar aryl linkers. We find that E-fields induce significant conformational changes in the linkers (twisting) that alters π-conjugation and, in turn, the magnetic J coupling between TOT radicals. In-plane E-fields twist the linkers toward the plane of the radicals, enhancing π-conjugation and increasing AFM coupling. Out-of-plane E-fields induce more orthogonal linker conformations and decrease the coupling strength. The magnetoelectric response depends on a combination of steric hindrance, π-conjugation, and polarization. Significant and measurable cumulative changes in J of up to 3.9 meV could be achieved by using in-plane and out-of-plane E-fields of up to 0.5 V/Å. In some cases, applied E-fields can also induce switching between paramagnetism and antiferromagnetism. Calculations on a 2D covalent organic framework (COF) based on a network of TOT radicals and dipolar linkers confirm that this approach is also viable for extended systems. Such COFS could also display E-field induced ferroelectric responses. Overall, our proof-of-principle study highlights the interplay between molecular structure, E-fields, and magnetism and establishes an innovative and chemically rational framework for developing all-organic magnetoelectric materials.