Proton-Triggered Hypsochromic Luminescence in 1,1'-(2,5-Distyryl-1,4-phenylene) Dipiperidine.

A proton-triggered hypsochromic luminescent chromophore 1,1'-(2,5-distyryl-1,4-phenylene) dipiperidine (DPD) was designed and synthesized. Upon treatment by hydrochloric acid (HCl), the emission of DPD showed a large hypsochromic shift in both THF solution and microcrystals. Theoretical calculations and powder X-ray diffraction experiments reveal that the switchable emission of DPD originated from the change of the distribution and the spatial arrangement of the frontier molecular orbitals, and the different stacking modes of DPD in microcrystals also contribute to the switchable emission of DPD in aggregates.