Photoinduced Radical Luminescence of Diazapyrene Derivatives upon Complexation with Cucurbit[<i>n</i>]uril Hosts

Molecular design with an electron donor-acceptor (D-A) structure and host-guest complexation are effective strategies for stabilizing radicals. Herein, we report the design and synthesis of cationic diazapyrene derivatives featuring a D-A structure, as well as the influence of host-guest complexation on their photoinduced organic radical photophysical properties. Compared to the methylated diazapyrene 1, the other three derivatives 2-4, containing triphenylamine, coumarin, and naphthalene units as D groups, respectively, are more favorable for the generation of radicals. Binding studies reveal that cucurbit[8]uril (CB[8]) forms 1 : 1 inclusion complexes with derivatives 2-4, while CB[10] forms a 2 : 2 inclusion complex with 2 and supramolecular polymers with 3 and 4. The radical luminescence of derivatives 1-4 in aqueous solution is significantly promoted upon complexation with CB[8] or CB[10]. Additionally, the emission color of 3 shifts from cyan to yellow-green upon light irradiation in the presence of CB[8].