High pressure effects on the luminescent properties and structure of coumarin 153

The absorption and emission spectra of coumarin 153 (C153) at high pressure have been detected up to 7.0 GPa. Because of the strong electron-withdrawing group at 7 site in the coumarin, the fluorescence spectrum of the title compound exhibits one band emission at ambient pressure from its charge transfer (CT) state. At higher pressure, the decreased distance of the crystal face, as proved by in situ x-ray diffraction measurement, and the increased interactions between the molecules enhance the energy gap between the local excited (LE) state and the CT state. Two-band emissions of C153, from LE and CT, respectively, have been observed.