Pressure-modulated intermolecular charge transfer in a cocrystal to achieve tunable luminescence

Cocrystal engineering offers the opportunity to achieve noncovalent synthesis of functional molecules with tunable luminescent features. In this study, Pe-4F2CN co-crystal was fabricated by using perylene (Pe) and tetrafluoroterephthalonitrile (4F2CN) through charge-transfer (CT)-induced assembly. The co-crystal exhibits two distinct emission bands and pronounced piezochromic properties, achieving the tunable luminescence from yellow to red upon compression. By the analysis of crystal structure and high-pressure IR spectroscopy combined with theoretical calculations, it revealed that the enhanced π-π and C-H···N interactions would regulate the charge-transfer process, thereby leading to the redshifts in photoluminescence (PL) and decreased emission intensity. This research not only demonstrates a novel approach to achieving tunable luminescence through pressure modulation, but also deepens the understanding of the relationship between intermolecular interactions and photophysical properties, which provides further guidance for the design of piezochromic materials.