Design Strategies for the Construction of Visible-to-NIR Light Triggered Diarylethenes.

Abstract

Diarylethenes (DAEs) are a well-known class of photochromic compounds, known for their high thermal stability and excellent fatigue resistance. However, traditional DAEs typically require ultraviolet (UV) light to activate their photochromic behavior, which limits their applicability in biological and practical systems due to potential UV-induced photodamage and poor tissue penetration. To overcome these challenges, significant efforts have been made to develop molecular switches that can be triggered by visible and NIR light due to their high tissue penetration and comparably less cell damage properties. Despite the escalating interest and swift advancements in this field, a comprehensive review on molecular designing strategies that enable visible and NIR triggered DAE-based organic systems still remains scarce. This review presents a comprehensive overview of all reported photoswitchable DAEs responsive to visible and NIR light published over the past 7 years (2018-2025). It highlights intricate modular design strategies, such as π-extended conjugation, photoinduced electron transfer, two-photon absorption, nanoparticle-mediated upconversion, and supramolecular assembly, supplemented with tabulated and comprehensively curated data on the photochromic properties of each compound. By detailing design approaches and structure-function relationships, this review provides a clear and integrated understanding of strategies to achieve visible and NIR-triggered photochromism in DAE-based molecules and outlines future directions for the field.