Oxidation of ophthalmic drugs photopromoted by inorganic radicals
The rate constants of the reactions of the sulfate (SO4−) and hydrogen phosphate (HPO4−) radicals with the imidazoline derivatives naphazoline, tetrahydrozoline, oxymetazoline, xylometazoline, and the model compound 2-methyl-2-imidazoline (IZ), were measured by flash-photolysis. The experimental values of these rate constants are on the order of 108–109 M−1 s−1. The reactions with the sulfate radicals proceed by an initial attack on the aromatic rings, which leads to the formation of N-centered radicals of naphazoline and to phenoxyl radicals of the other substrates. The experimental absorption spectra of the intermediates were compared to those obtained from theoretical time-dependent density functional calculations with explicit account for bulk solvent effects.
► The imidazoline derivatives react with SO4− and HPO4−. ► The reactions with SO4− proceed by an initial attack on the aromatic rings. ► N-centered radicals of naphazoline are obtained. ► N-centered radicals and phenoxyl radicals are formed for the other ophthalmic drugs.
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 244, 15 September 2012, Pages 32–37