Pyrazine derivatives DIPY , TETPY and CNDIPY have been designed and synthesized which form fluorescent supramolecular assemblies in mixed aqueous media due to their AIEE and ICT characteristics. Among all the derivatives, the assemblies of TETPY and CNDIPY show strong absorption in the visible region with high absorption coefficients, low HOMO-LUMO gap, and high photostability. Further, the supramolecular nanoassemblies of TETPY and CNDIPY show excellent potential to generate reactive oxygen species (ROS) under the visible light irradiation. Owing to their strong absorption in the visible region and ROS generation ability, the supramolecular nanoassemblies of TETPY and CNDIPY act as efficient photoredox catalytic systems for carrying out (a) oxidative amidation of aromatic aldehydes (b) hydroxylation of boronic acid and (c) oxidative homocoupling of benzylamines under mild conditions such as aqueous media, aerial environment, and natural sunlight as a source of irradiation. All the mechanistic investigations suggest the participation of in-situ generated ROS in the organic transformations upon light irradiation.

Supramolecular nanoassemblies of an AIEE-ICT-active pyrazine derivative (TETPY) having strong absorption in the visible region and excellent transportability have been utilized as an efficient photoredox catalytic system for the synthesis of a variety of benzimidazoles having electron-withdrawing/electron-releasing/aliphatic groups under “metal-free” conditions. The reaction protocol involves the successful harvesting of visible light by TETPY assemblies to catalyze the coupling of o-phenylenediamine/substituted diamines and substituted aromatic/heterocyclic/aliphatic aldehydes under aerial conditions using mixed aqueous media as the reaction solvent. TETPY assemblies could activate aerial oxygen to generate superoxide for completing the vital proton abstraction step without the need for any external metal/base/oxidant. Moreover, all the products are purified by recrystallization from organic solvents. The TETPY assemblies also exhibited high efficiency in catalyzing the synthesis of 2-substituted benzothiazoles and quinazolines in excellent yields.