Irradiation-wavelength dependent photochemistry of the bichromophoric sulfonylurea chlorsulfuron

The photochemistry of the bichromophoric sulfonylurea chlorsulfuron has bee n investigated at different irradiation wavelengths and environmental condi tions. The identified products indicate that different reaction paths are f ollowed, depending whether the benzene or the triazine component chromophor es are excited. In the first case, the chlorine atom is substituted by hydr ogen or hydroxyl in water; in the second one three competitive photodegrada tion paths may be followed, the most efficient one being the cleavage of th e S-N bond in the sulfonylurea bridge. Photodegradation quantum yield measu rements, combined with laser flash photolysis experiments have shown that, while both singlet and tripler states contribute to all photolytic paths in deaerated solution, quenching by oxygen makes the triplet contribution neg ligible in samples equilibrated with air. (C) 2001 Elsevier Science B.V. Al l rights reserved.