Fig. 3

UV–Vis spectra for reaction monitoring. a UV–Vis spectra of the solution of precursors and the products, 1 and 2. b Increased absorbance of 1 and 2 over the precursors. c Time-dependent UV–Vis spectra. d Increased absorbance of the reaction solution for synthesizing 1 without adding Ag₂CO₃. e Increased absorbance of the reaction solution for synthesizing 1 with adding 4% amount of Ag₂CO₃, and f Increased absorbance at 330 nm (solid lines) and 370 nm (dash lines) upon time for two parallel reaction solutions with or without adding 4% amount of Ag₂CO₃