Amplified Light-Induced pK(a) Modulation with Diarylethene Photoswitches.

The reversible modulation of acidity using molecular photoswitches enables the remote control of a variety of (bio)chemical processes with light. Herein we investigated the structural features that allow amplifying photoinduced pK(a) variation in phenol-diarylethene conjugates, which toggle between low- and high-acidity states by switching the conjugation between the ionizable moiety and electron-withdrawing groups upon photoisomerization. By tuning the structure of these conjugates, high pK(a) modulation amplitudes were accomplished that surpass those previously reported.