Lights on 2,5-diaryl tetrazoles: applications and limits of a versatile photoclick reaction

Recently, photoclick chemistry emerged as a powerful tool employed in several research fields, from medicinal chemistry and biology to material sciences. The growing interest in this type of chemical process is justified by the possibility to produce complex molecular systems using mild reaction conditions. However, the elevated spatio-temporal control offered by photoclick chemistry is highly intriguing, as it expands the range of applications. In this context, the light-triggered reaction of 2,5-diaryl tetrazoles with dipolarophiles emerged for its interesting features: excellent stability of the substrates, fast reaction kinetic, and the formation of a highly fluorescent product, fundamental for sensing applications. In the last years, 2,5-diaryl tetrazoles have been extensively employed, especially for bioorthogonal ligations, to label biomolecules and nucleic acids. In this review, we summarized recent applications of this interesting photoclick reaction, with a particular focus on biological fields. Moreover, we described the main limits that affect this system and current strategies proposed to overcome these issues. The general discussion here presented could prompt further optimization of the process and pave the way for the development of new original structures and innovative applications.