Mechanofluorochromism of pyrenyl acrylates with different substitutional position and steric hindrance

Solid-state emission color change upon mechanical stimuli, known as mechanofluorochromism (MFC), is reported for pyrenyl acrylates. The C-1- and C-4-alkenylated pyrenes ((E)-Ethyl-3-(Pyren-1-yl)acrylate and (E)-Ethyl-3-(Pyren-4-yl)acrylate, respectively) exhibited distinct MFC behaviors (hypsochromic and bathochromic shifts). The introduction of bulky tert-butyl groups in 2,7-position ((E)-Ethyl-3-(2,7-Di-tert-butylpyren-4-yl)acrylate) also induced the shifted overlapping of pyrene moiety in pristine form and suppressed the thermal back reaction in ground form. These characteristic MFC behaviors of pyrene-derived acrylates are discussed on the basis of emission spectra and decay times in pristine and ground forms.