Supramolecular Rh6 catalytic system promoting directed [4+4] cycloaddition reaction of anthracene under UV irradiation

摘要

Herein, two new organometallic triprisms catalytic systems, 1, 2 were successfully constructed by the reaction of edge arm units E1, E2 and a tridentate ligand 4, 4', 4"-(1H-imidazole-2, 4, 5-triyl) tripyridine (L1), respectively through the coordination-driven self-assembly strategy at room temperature. The structural configuration of triprisms 1 and 2 were determined by X-ray crystallography in combination with NMR spectroscopy. And a carefully structural analysis shows that there exists an obvious and ordered supramolecular pockets based on accumulation effect of these discrete triprisms, which could accommodate appropriate guest molecules by space effect and supramolecular interactions including hydrgen bonding and hydrophobic interactions. Interestingly, anthracene (ANT) molecules could be wrapped in the confined pockets to form stable ANT@1 complex in solution, which could be confirmed forcefully by UV-vis and H-1 NMR spectra. Notably, when the ANT@1 was irradiated in methanol under UV light of 365 nm, a new set of NMR peaks appeared, well matching these signals of di-paraanthracene, clearly demonstrating the occurrence of [4 + 4] cycloaddition reaction. This research provides a new idea for photodimerization of ANT into di-paraanthracene.

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