“…0.4 g of 2 (1.8 mmol) and 0.3 g of 4 (1 mmol) were added to a 100 mL roundbottomed flask containing 20 mL of absolute ethanol and 0.5 mL of piperidine; the reaction mixture was stirred at 80 °C for 4 h under N 2 protection, and then, the mixture was subjected to rotary evaporation and purified by column chromatography (DCM/MeOH/HAc = 100:1:1, v/v/v) to afford KQ−SO 2 as a purple solid with a yield of 80%. 1 H NMR (400 MHz, DMSO-d 6 ): 9.14 (s, 1H), 8.68−8.64 (d, J = 16.0 Hz, 1H), 8.41−8.39 (d, J = 8.0 Hz, 1H), 8.28−8.26 (d, J = 8.0 Hz, 1H), 7.89−7.85 (dd, J 1 = 8.0 Hz, J 2 = 4.0 Hz, 3H), 7.74−7.61 (t, J = 26.0 Hz, 2H), 7.61−7.57 (m, 3H), 7.40−7.36 (t, J = 8.0 Hz, 1H), 4.59−4.54 (dd, J 1 = 8.0 Hz, J 2 = 4.0 Hz, 2H), 4.17 (s, 3H), 1.65 (s, 6H), 1.40−1.36 (t, J = 8.0 Hz, 3H); 13 Spectrophotometric Measurements. Fluorescence measurement experiments were measured in 10 mM phosphate buffer solution with DMSO as cosolvent solution (H 2 O/DMSO = 99:1, v/v).…”