Engineering Flexible Multi-Component Molecular Crystals with Variable Co-former Bridges and Tunable Photophysical Properties

Molecular crystals, with their exceptional structural tunability, provide a multifunctional platform for accessing diverse emergent properties, spanning mechanical and optical behaviors. Here, we report a supramolecular design strategy to engineer elastically flexible multicomponent molecular crystals (MCCs) with tunable photophysical responses. A systematic variation in co-former chain length and conjugation within acridine (ACD) and phenazine (PHZ) based MCCs yielded a series of five elastically bendable crystals. Structural analysis by single-crystal X-ray diffraction and µ-focus synchrotron XRD revealed that mechanical bending induces anisotropic compression and expansion across the crystal, accompanied by modulation of π-π stacking distances and molecular orientations. Spatially resolved photophysical mapping using confocal fluorescence and fluorescence lifetime imaging microscopies uncovered a direct correlation between local mechanical strain and emission behavior. These findings elucidate the structure-property relationships governing stress-induced photophysical modulation and establish a design paradigm for soft, luminescent crystalline materials for future flexible optoelectronic and sensing applications.