Synthesis and Photophysical Properties of Cyclic Homodimer of U-Shaped Dibenzophenazinylene

A new class of cyclic π-extended heteroarylene oligomer─cyclic homodimer of U-shaped dibenzophenazinylene─has been successfully synthesized and characterized. NMR spectroscopy and DFT calculations implicated the unique topologies of the macrocycle. The cyclic dimer displays intense green-to-yellow fluorescence in both solution and the solid state. Remarkably, it shows acid-responsive color changes and a photoluminescence "turn-OFF" response upon protonation. The heteroaromatic macrocycle represents a versatile scaffold for the development of advanced optoelectronic materials and supramolecular host-guest systems.