General procedure for the synthesis of 5-formyl-1,10-phenanthroline from 5-methyl-1,10-phenanthroline: 5.15 mmol of 5-methyl-1,10-phenanthroline and 12.43 mmol of selenium dioxide were dissolved in 80 mL of o-dichlorobenzene, and the reaction was carried out at reflux for 4 hours. After completion of the reaction, it was cooled to room temperature and filtered through diatomaceous earth. The filtrate was extracted with 200 mL of 1 mol/L hydrochloric acid solution, and the aqueous phase was separated and collected. Subsequently, the aqueous phase was back-extracted five times with 250 mL of dichloromethane. After adjusting the pH of the aqueous phase to neutral, the organic layer was collected. 0.5 g of anhydrous magnesium sulfate was added to the organic layer for drying, shaken well and allowed to stand for 20 minutes. The desiccant was removed by filtration and the filtrate was concentrated and dried by rotary evaporator to give 0.753 g of 5-formyl-1,10-phenanthroline in 69.72% yield.
