Multi-stimuli-responsive fluorescence switching from a novel organic polymorphic benzoimido-benzamide derivative

Abstract

A novel organic polymorphic luminogen, (Z)-N-((benzoylimino) (4-(diphenylamino)phenyl)methyl)-N-(4-fluorophenyl)benzamide (DPA-PYZ-F), has been designed and synthesized successfully by a green photo-oxidation reaction. Two polymorphs (FB and FG) based on DPA-PYZ-F with different conformations display blue and green fluorescence, respectively. The emission of the newly obtained polymorphic molecule can be switched through the response to a mechanical force, thermal stimulus and protonic acid. The photophysical property tests and single crystal structural analysis disclosed that the mechanical force stimuli-responsive behavior of the FB and FG samples originate from the change of molecular arrangement. More significantly, FT-IR spectroscopy confirmed that the conformation transition from the FG to the FB could be achieved by thermal stimulus at 430 K. Additionally, protonation−deprotonation of the benzoylimino moieties in DPA-PYZ-F induced a remarkable fluorescence on-off characteristics upon protonic acid and thermal stimulus. The multi-stimuli response performance endows the new kind of molecule with the potential as a candidate for applications in mechanical force, thermal and protonic acid sensing.