Sensitive Detection of Spin-Electric Coupling in a Cr3 Antiferromagnetic Triangle

Abstract

Molecular antiferromagnetic triangles are a convenient platform to study the effect of an electric field on the magnetic exchange interactions. However, such effects are typically hard to detect, especially in systems with weak spin–orbit coupling. In this work, an asymmetric μ₃-oxo-centered Cr₃ triangle was synthesized and structurally characterized as a non-centrosymmetric molecular crystal suitable for probing Spin Electric Coupling (SEC). A combination of single-crystal magnetometry, cantilever torque magnetometry, and continuous-wave electron paramagnetic resonance (EPR) allowed precise determination of the spin Hamiltonian, including the small Dzyaloshinskii–Moriya interaction. Electric-field-modulated EPR (EFM-EPR) experiments provided the first direct observation of SEC in a Cr^III-based complex, revealing measurable electric-field effects on the single-ion g tensor and setting an upper bound for the SEC influence on magnetic exchange interactions. These findings demonstrate the exceptional sensitivity of EFM-EPR spectroscopy for quantifying SEC and highlight the crucial role of molecular symmetry and ligand environment in enabling electric control of spin states, thus advancing the rational design of molecular systems for quantum technologies.