Consecutive and Extensive Transition of Luminescent Color of an Organic Solid Material by Applying High Pressure

By compressing the organic solid luminescent material 2,7-di­(naphthalen-1-yl)­fluorenone (1-DNFO), a consecutive and massive modulation of its UV–vis absorption and photoluminescence spectra has been achieved. In particular, the photoluminescence peak shifts from the visible (548 nm) to the near-IR region (879 nm). In situ high-pressure synchrotron X-ray diffraction studies indicate that the tremendous photoluminescence redshift of 1-DNFO with a parallel packing mode results from the enhancement of intermolecular interaction, which is caused by the decrease of unit cell volume and intramolecular dihedral angle. Additionally, a time-dependent density functional theory study shows that the enhancement of intermolecular interaction under high pressure should be responsible for the dramatic redshift of the absorption and emission spectra. For comparison, the analogue 2,7-di­(naphthalen-2-yl)­fluorenone (2-DNFO) with an interlaced packing mode shows the relatively small-scale photoluminescence redshift under compression, due to the difference of molecular arrangements. Our research manifests that the optical properties of organic optical crystals with effective π···π interaction are more sensitive to external pressure, which may have the potential application for multicolor luminescent materials and devices.