Remarkable responsive behaviors of iso-aminobenzopyranoxanthenes: protonation effect, photochromism and piezochromism.

Abstract The iso -cis/trans-aminobenzopyranoxanthenes (iso -cis/trans-ABPXs), as one of popular leuco dyes, were investigated in solution or crystal phase. The introduction of benzo-pentacyclic-ester group in iso -cis/trans-ABPXs leads to remarkable multi-stimuli responsive behaviors, including protonation effect, photochromism and piezochromism with notable color changes. The iso -cis/trans-ABPXs show different in the responsive sensitivity and the iso -cis-ABPX is highly sensitive to environmental stimuli relative to the trans-form, which can be explained by their different C-H⋯O interaction and/or C-O bond length. Interestingly, as the ultraviolet light irradiation time increasing, the iso -cis/trans-ABPXs solution gradually becomes transparent and orange precipitates are achieved, which is identified as iso -ABPXs±. Multi-stimuli responsive behaviors on the iso -cis/trans-ABPXs provide a comprehensive insight into the chromogenic mechanisms of this type of materials, suggesting that they may be potential candidate materials for sensors and indicators. Graphical abstract Image 1 Highlights • The iso -cis/trans-ABPXs show remarkable color and spectral changes under different stimuli respectively. • The iso -cis -ABPXs is more sensitive to the stimuli due to the differences in structures. • The orange solid of iso -cis/trans-ABPXs± can be produced from iso -cis/trans-ABPXs solution under the UV light irradiation. [ABSTRACT FROM AUTHOR]