2,1,3-Benzothiadiazoles Are Versatile Fluorophore Building Blocks for the Design of Analyte-Sensing Optical Devices

BTDs (2,1,3-benzothiadiazoles) are fluorescent heterocycles widely used in different applications, including biomarkers, sensing optical devices, OLEDs, organic transistors, and solar cells. This review mainly focuses on the current progress in the design of compounds derived from the BTD core, aiming for their use as chromogenic and/or fluorogenic devices for detecting anionic, cationic, and neutral analytes. Reactions and synthetic strategies that show the synthetic versatility of BTDs are initially presented, to provide a better understanding regarding the assembly of optical detection systems. The photophysical mechanisms of the detection are also described. A discussion is also presented on the target analytes for which the optical detection devices based on BTD were planned. The examples discussed here will offer the sensors community perspectives for developing new optical detection devices based on BTD for different types of analytes of importance for the most diverse areas of knowledge.