Pressure-Induced Controllable Multicolor Emission in Ethyl 7-hydroxy-2-oxo-2H-chromene-3-carboxylate

Organic piezochromic materials represent an important class of stimulus-responsive materials with broad prospects for pressure-sensing applications. The achievement of high sensitivity and a large color contrast under external stimulation is key to broadening their practical applications. In this work, the piezochromic behavior and phase transition of ethyl 7-hydroxy-2-oxo-2H-chromene-3-carboxylate (EHC) were reported. At 1.0 GPa, EHC undergoes a pressure-induced phase transition, and as the pressure increases, it exhibits controllable multicolor emission shifting from blue to green and then to yellow. Below 1.0 GPa, EHC exhibited a sensitivity of 1.12 nm·GPa^-1 and a color contrast of 1 nm. After the phase transition, these values were significantly increased to 11.63 nm·GPa^-1 and 186 nm, respectively, demonstrating its potential as an excellent colorimetric sensor for external pressure. This enhancement can be attributed to pressure-enhanced intermolecular interactions, in which strengthened π-π interactions are expected to play a key role. In summary, this work provides valuable insights into the relationship between molecular optical properties and structure, and also facilitates the development of new piezochromic luminescent materials.