Visible to near-infrared light activated photoacids: Molecular architecture for chemical and biological applications

Abstract

Photoacids (PAs) are compounds capable of modulating proton concentration in response to light. PAs have evolved to address the limitations of UV light, which include phototoxicity and shallow tissue penetration. The shift towards PAs activated by visible to near-infrared wavelengths offers several advantages such as deeper tissue penetration, reduced phototoxic and enhanced environmental sustainability. These PAs allow for precise control over reaction conditions and are crucial for applications in biomedicine and materials science. The classification of these PAs includes photolytic, excited-state, and photoisomerized types, each with unique properties for light absorption and acid generation. Strategies for functional enhancement of these PAs are summarized, such as introduction of electron-donating and withdrawing substituents, enlargement of the conjugated system, incorporation of D-π-A structures, and enhancement of two-photon absorption cross-sections. These strategies are essential for improving photoacidic performance in applications like photocatalysis, drug delivery, and photoacid therapy. Besides, the impediments to the practical utilization of PAs across various domains are discussed as well.