Optical properties and mechanofluorochromism of new BODIPY dyes based on the pyridine-pyrimidine hybrid structure

A new family of BODIPY dyes (PPB1-4) based on the pyridine-pyrimidine hybrid structure has been synthesized. These dyes show high cyan fluorescence in hexane with quantum yields (Φ_f) ranging from 0.33 to 0.90. Interestingly, moderate fluorescence of PPB1-4 is observed in the solid state (Φ_f, 0.11-0.26). X-ray structure analysis demonstrates that H-aggregation should be responsible for the red-shifted and quenched emission in the solid state. Moreover, PPB1-4 show high contrast and reversible mechanochromic fluorescence based on the proposed mechanism of mechanical stimuli triggered dimer dissolution and formation. In addition, rewritable mechanochromic fluorescence recording media fabricated with PPB4 have been successfully achieved.