Phthalazine is a heterocyclic compound with the molecular formula C8H6N2 composed of a benzene ring fused with a pyridazine ring. Phthalazine and its derivatives do not exist in nature. Phthalazines are used as starting materials for organic synthesis. Studies have found that phthalazine has a variety of physiological activities, such as anti-cancer, antibacterial, anti-inflammatory and so on. The synthesis of phthalazine compounds with novel structures and better biological activities has become a research hotspot in recent years.
The two N atoms in Benzothiadiazole could possibly form intermolecular hydrogen bonding, leading to a more planar backbone. Benzothiadiazole is a strong electron-accepting molecular fragment. By fusing it with thiazole donor-acceptor dyes, near-infrared fluorescence was created. The benzothiadiazole ring is a useful n-type building block for designing electron-transport materials for organic and polymer light-emitting diodes (LEDs). Arene- and heteroarene-fused thiadiazoles have also found use in the design of low-band-gap materials for the construction of organic field-effect transmitters (OFETs), as stable organic radicals, and as one or two photon-absorbing materials for the design of nonlinear near-infrared (NIR) dyes. Benzothiadiazoles acting as the electron-accepting cores have been incorporated into dendrimer-type light-harvesting materials.