Pressure-Dependent Structural and Luminescence Properties of 1-(Pyren-1-yl)but-2-yn-1-one

The crystal structure of 1-(pyren-1-yl)but-2-yn-1-one (1a, a polynuclear aromatic hydrocarbon displaying enhanced luminescence in the solid state, has been re-determined at several pressures ranging from atmospheric up to 3 GPa using a Diamond Anvil Cell (DAC). These experiments were augmented by periodic DFT calculations at pressures up to 4.4 GPa. UV-Vis fluorescence of 1a at non-ambient pressures has also been investigated. The crystal structure consists of infinite -stacks of anti-parallel 1a molecules with discernible dimers, which may exemplify aggregates formed by pyrene derivatives in solution and thin films, and is predominantly stabilized by dispersion. The average inter-planar distance between individual molecules within -stacks decreases with pressure in the investigated range. This results in piezochromic properties of 1a: a red-shift of sample color, as well as a bathochromic shift of fluorescence with pressure (by ca. 100 nm at 3.5 GPa). Two-component fluorescence spectra support the hypothesis that at l east two types of excimers are involved in the electronic excitation processes in crystalline 1a.