Fluorescence response of anthracene modified D-π-A heterocyclic chromophores containing nitrogen atom to mechanical force and acid vapor

Abstract Three new 9-vinyl anthracene derivatives functionalized naphthalene (ANNP), quinoline (ANQL) and quinoxaline (ANQX) have been synthesized, and they exhibit excellent solid state luminescence. Optical properties and quantum chemical calculations indicate the absence of D-π-A structure in ANNP, and the presence of typical D-π-A structures in ANQL and ANQX. Though the differences between the three molecules are marginal, their stimuli-responsive behaviors are contrasting. Non-heteroatom-assisted ANNP has no clear chromic property. In contrast, heteroatom-assisted ANQL and ANQX show a clear response to external stimuli such as mechanical force (mechanofluorochromism) and protons (acidofluorochromism). On one hand, both of them exhibit contrasting MFC effects. Upon grinding, emission wavelength shifts are 16 nm and 28 nm, respectively. ANQX shows a large spectral change, which might be originated from nitrogen atom induced ICT process and twisted molecular conformation. On the other hand, two molecules show difference acidofluorochromic response. The presence of nitrogen atom leads to the formation of a stable complex between target molecule and TFA. The solution and film of ANQX achieve a fast response to TFA with high sensitivity and low detection limit. The present results suggest that the anthracene modified D-π-A heterocyclic chromophores containing nitrogen atom can achieve fluorescence response to mechanical forces and acid vapor.