Benzofuranone-based spiropyrans: synthesis, temperature-dependent photochromic properties, and DFT calculations†

The photochromic behaviors of spiropyrans that are fused with an aromatic ring adjacent to the spirocarbon have not been well studied. A series of benzofuranone-based spiropyrans containing a thiophene, benzothiophene, selenophene, or indole ring close to the spirocarbon center were synthesized through rhodium(iii)-catalyzed annulation of hydroxyl 1,2-diarylethane-1,2-diones with internal alkynes. Their temperature-dependent photochromic properties were observed experimentally and explained by density functional theory (DFT) calculations.