2,1,3-Benzothiadiazole and Derivatives: Synthesis, Properties, Reactions, and Applications in Light Technology of Small Molecules

2,1,3‐Benzothiadiazole (BTD) is one of the most important nuclei used in the chemistry of photoluminescent compounds and applicable for light technology. The understanding of its properties and reactions is fundamental for the design and application of these derivatives in molecular organic electronic devices and for other technologies. As a result of their potential as constituents of organic light‐emitting diodes, solar cells, liquid crystals, dyes, photovoltaic cells, and many others, attention has been focused on BTD π‐extended derivatives with potential use in this exciting area. Herein, we describe their syntheses, properties, reactions, and selected examples of applications in light technology using by BTD (small molecules) as the core. Molecular 2,1,3‐benzothiadiazole (BTD) is an important nucleus used in the chemistry of photoluminescent compounds and applicable for light technology. Its properties and chemical reactivity are fundamental for the design of organic electronic devices. BTD derivatives can be used as constituents of organic light‐emitting diodes, solar cells, liquid crystals, dyes, photovoltaic cells and many others, and these compounds represent an exciting area of study.