Rational structural design of aromatic Azo photoactive small molecules for biomedical applications

Aromatic Azo molecules, including azobenzenes (Ph–NN–Ph) and heteroaryl Azo (Het–NN–Ph or Het–NN–Het), have emerged as versatile and high-performing photoactive switches for biomedical applications. Despite decades of extensive research on aromatic Azo as molecular photoswitches, the full translational potential of these small molecules remains underexploited. This review systematically outlines structural design strategies for aromatic Azo, spanning from functional substituent engineering to π-conjugation modulation, to fine-tune its photophysical properties. We summarize state-of-the-art synthetic methodologies for crafting multifunctional aromatic Azo frameworks, contrast the distinct isomerization mechanisms of azobenzenes versus heteroaryl Azo derivatives, and highlight the latest biomedical application advances, including biological imaging and detection, drug delivery, photopharmacology, phototherapy, miscellanea photo responsive biomaterials and constructs, and control in chemical biology. Furthermore, we discuss clinical translation challenges and opportunities in this field, proposing innovative strategies to address critical issues. This review aims to substantially advance the burgeoning field of aromatic Azo photoactive small molecules for biomedical applications.