Substituent Effect on Metastable-State Photoacids: Design, Synthesis and Evaluation of their Photochemical Properties.

Recently, metastable-state photoacids have been widely used to control proton transfer in numerous chemical and biological processes as well as applications with visible light. Generally, substituent groups have great influence on photochemical properties of molecules, which will further affect their applications. Yet, substituent effect on the metastable-state photoacid has not been studied systematically. In this work, sixteen metastable-state photoacid derivatives were designed and synthesized based on substituents involving a large range of σ-π electron-donor-acceptor capability. Substituent effects main on their color display (or maximum absorption peak(s)), solubility, pKa(s), dark-/photo-acidity, photosensitivity and relaxation kinetic(s) were investigated in detail. This study will be conducive to targetedly design and synthesize promising photoacids as well as to apply their photo-controlled proton-release processes in functional materials/devices.