Ratiometric Chemosensors That Are Capable of Quantifying Hydrostatic Pressure Stimulus: A Case of Porphyrin Tweezers

Investigating chemosensors that are capable of quantifying pressure in solution, particularly hydrostatic pressure, which is one of the mechanical forces, is an attractive challenge in chemistry from the viewpoint of "mechano"-science. Herein, we report the investigation of chiral porphyrin tweezers, Por-Cy and Por-DPhEt, comprising different flexible linkers; Por-Cy and Por-DPhEt displayed distinct ratiometric signaling by using the higher excited S₂ state with a standard excited S₁ level. A novel operative mechanism using the S₁/S₂ fluorescence ratio was revealed using hydrostatic pressure-ultraviolet/visible (UV/vis), fluorescence/excitation, circular dichroism spectroscopy, and lifetime measurements, which can be further controlled by the open-closed conformational change inherent in the tweezer skeleton. Furthermore, the fluorescent chiral tweezers exhibited a promising |g _lum| of 2.9 × 10^-3, indicating that they are potential candidates for sensory applications in chiral environments. This study provides opportunities for the development of smart pressure-responsive chemosensors.