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.