Thalidomide-Photoswitch3-NH2 hydrochloride is essential in creating PHOTACs, which are PROTACs activated by specific light wavelengths. These compounds become inactive in darkness and switch to an active cis isomer state under 390 nm irradiation, while wavelengths above 450 nm reverse this activation. This compound comprises a CRBN-recruiting ligand, an azobenzene photoswitchable crosslinker, and a pendant amine that interacts with an acid on the target warhead, and is used to synthesize PHOTAC-I-10 and PHOTAC-II-6.