Recent Advances in Visible Light-Triggered Azobenzene Photoswitches (A Review)

Abstract

Reversible molecular photoswitches, which undergo controlled transitions between well-defined isomeric states, constitute essential building blocks for advanced photoresponsive systems. Although azobenzene (AB) derivatives represent a prototypical class of such switches, their traditional activation by UV irradiation imposes critical constraints, notably limited penetration depth in biological tissues/materials and potential photodamage effects, thereby hindering their widespread implementation. These inherent limitations have stimulated intensive research into visible light-triggered AB photoswitches, opening new avenues for diverse applications across materials science and biomedical fields. This review systematically outlines molecular design strategies for achieving visible light-driven isomerization in AB derivatives, including: para-substituted azobenzenes, bridged azobenzenes, ortho-substituted azobenzenes, azoheteroarenes, BF₂-coordinated azobenzenes, two-photon absorption, and upconverting nanoparticles. Furthermore, we critically examine existing challenges and propose future directions for developing AB derivatives that can be activated within the biologically favorable 650–900 nm “phototherapeutic window.”