Acid-Stimuli-Luminescence and Carbonyl-Proton Interaction Dependent Emission Properties of 2,6-Biphenyl-4-pyrone Crystals

The diversity of hydrogen and ionic bond interactions in 2,6-biphenyl-4-pyrone-acid (BPP–acid) supramolecular systems and the acid-induced luminescence character of BPP was reported. On the basis of X-ray single crystal structure analysis and theoretical calculation, the strong luminescence of BPP–HCl and BPP–TFA (TFA = trifluoroacetic acid) crystals was attributed to the protonation or strong hydrogen bond interactions between the carbonyl group of BPP and the proton of HCl or TFA. Notably, in BPP–TFA crystal the interaction between BPP and TFA displayed a “mixed bond” feature; namely, the bond between carbonyl of BPP and hydroxyl of TFA possesses partial hydrogen bond and partial ionic bond nature. The acid stimuli-luminescence properties of BPP film may offer a potential application in chemical sensors