Antiaromaticity as a Design Principle for Magnetically Enhanced Chiroptical Anisotropy

Enhancing chiroptical response at low excitation energies remains a central challenge for small organic molecules because their lowest excited states are typically dominated by an electric-dipole character. Here we demonstrate that antiaromaticity can be exploited as a molecular design principle to access low-energy excitations with enhanced magnetic contributions. By fusing a planar paratropic s-indacene (4nπ) core with [5]helicene scaffolds, we construct a helically chiral antiaromatic system that exhibits pronounced dissymmetry factors gabs reaching 10-2 in the short-wave near-infrared region. Combined GIMIC/NICS analysis and multilevel electronic-structure calculations reveal that paratropic ring currents bias the frontier excited-state manifold toward enhanced magnetic contributions, while thermally induced symmetry breaking renders these states optically observable. These findings support the integration of antiaromatic cores with suitable chiral fusion topologies as a viable strategy for engineering chiroptical anisotropy.