General procedure for the synthesis of 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine from 2,4,6-tris-tosyl-1,3,5-triazine: 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine (1.0 g, 2.8 mmol), acetic acid (24.85 mL), and concentrated sulfuric acid (1.58 mL) were added to a 100 mL round-bottomed flask and stirred for for 5 minutes. Subsequently, the reaction mixture was heated to 50 °C and a solution consisting of chromium trioxide (2.58 g) dissolved in a mixture of acetic acid (5 mL) and concentrated sulfuric acid (5 mL) was added slowly and dropwise. The resulting dark brown slurry was stirred overnight. Upon completion of the reaction, the reaction mixture was filtered and the solid residue was collected. The residue was redissolved in 2N sodium hydroxide solution and filtered to remove insoluble impurities. Finally, the filtrate was acidified with 6N hydrochloric acid to afford the white precipitated product 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine (H3TATB) in 60% yield. The product was characterized by 1H NMR (400 MHz, DMSO-d6): δ=8.80 ppm (d, J=8.5 Hz, 6H), 8.18 (d, J=8.5 Hz, 6H); mass spectrometry (ESI) analysis showed [M-H]- peaks, and molecular weights of 440.0800 for the calculated value of C24H14N3O6 and 440.0100 for the measured value.
