Stacking Offset Significantly Enhances the Magnetic-Field Modulation of Charge Transfer Spin States in Isomeric Organic Crystals

Abstract Organic functional crystals with specific responses to external stimuli have attracted increasing interest for applications in biomedicine, information encryption, and sensing technologies. Modulating the offset of intermolecular provides an effective strategy for designing such responsive materials. Herein, two organic charge transfer cocrystals with distinct π-π stacking arrangements are designed. A larger stacking offset weakens the exchange interaction between electron–hole pairs while enhancing electron–phonon coupling, thereby significantly amplifying the magnetic-field response of charge transfer spin states. Magnetic field dependent photoluminescence and dielectric constant are exhibited. This finding reveals the importance of π-π stacking arrangements in achieving external-field manipulation of spin states in organic cocrystals.