Dynamic Behavior of Molecular Switches in Crystal under Pressure and Its Reflection on Tactile Sensing

Molecular
switches have attracted increasing interest in the past
decades, due to their broad applications in data storage, optical
gating, smart windows, and so on. However, up till now, most of the
molecular switches are operated in solutions or polymer blends with
the stimuli of light, heat, and electric fields. Herein, we demonstrate
the first pressure-controllable molecular switch of a benzo­[1,3]­oxazine OX-1 in crystal. Distinct from the light-triggered tautomerization
between two optical states, applying hydrostatic pressure on the OX-1 crystal results in large-scale and continuous states
across the whole visible light range (from ∼430 to ∼700
nm), which has not been achieved with other stimuli. Based on detailed
and systematic control experiments and theoretical calculation, the
preliminary requirements and mechanism of pressure-dependent tautomerization
are fully discussed. The contributions of molecular tautomerization
to the large-scale optical modulation are also stressed. Finally,
the importance of studying pressure-responsive materials on understanding
tactile sensing is also discussed and a possible mechanotransduction
mode is proposed.