Synthesis, solvent-dependent emission and two-photon absorption of a triangular –[D–π–A]3– macrocycle
A large triangular arylene–ethynylene macrocycle featuring unique circularly arranged –[D–π–A]3– electronic characteristics is designed and synthesized. The shape-persistent π-conjugated backbone is composed of alternating electron-rich dialkoxyphenanthrene and electron-deficient dicyanodibenzo[f,h]quinoxaline units, connected by ethynylene linkers. The synthesis of such a special macrocyclic molecule is realized by employing a post-cyclization functional group installation strategy. The absorption and emission spectra of the macrocycle are found sensitively dependent on the solvent polarity. By virtue of a conjugated π-scaffold and a cyclic –[D–π–A]3– motif, evident two-photon absorption (2PA) and two-photon excitation fluorescence properties are exhibited, with a 2PA cross section maximum of 3 × 103 GM determined by the Z-scan method.