Efficient and Reusable Benzimidazole Based Sulphonic Acid Functionalized Porphyrin Photocatalyst for C–N Bond Formation Under Visible Light Irradiation.

Synthesised N-substituted heterocyclic derivatives have ubiquitous applications in fine chemicals, pharmaceuticals, organic electronic materials, and agrochemicals. Numerous reports of photocatalytic C–N coupling in aid of a 5 W visible light source are documented in the literature which facilitates the cost reducibility, reusability, and promising methods for reaction. In this present work, we have designed and synthesised a benzimidazole-based sulphonic acid functionalized porphyrin photocatalyst (BSAFPPc) and confirmed by analytical techniques such as FT-NMR, FT-IR, and SEM/EDX. The BSAFPPc demonstrated an optical energy gap of 1.12 eV by using DRS. Further, the acidic potential was scrutinized by the Hammett acidity function which is H0 = 0.99. The BSAFPPc was used for the C–N coupling of morpholine, and inactivated aryl halides comprising electron-donating (–NH2, –OMe, –CH3) and withdrawing groups (–CHO, –NO2). This photocatalytic reaction produced an excellent practical yield from 60 to 90%. Further, the scope was extended to benzimidazole, pyrrole, indole and 1,2,4-triazole. The reaction has been experimented in an in-house homemade reactor system in a presence of a 5 W visible light source in an additive-free environment at ambient conditions. The photocatalyst was durable up to six photocatalytic cycles. The photocatalyst maintained its heterogenous nature which was asserted by the leaching test. [ABSTRACT FROM AUTHOR]