Abstract
Despite the number and variety of their biological applications, the mechanisms of action of the photoactive naphthalenic imides have not yet been fully elucidated. In order to provide mechanistic insight, the photochemistry of several N-substituted 1,8-naphthalimides (NI) and 1,4,5,8-naphthaldiimides (NDI) has been studied using absorption and fluorescence spectroscopy and by laser flash photolysis (λexc = 355 nm). The lowest singlet state (S1) is mainly ππ* in nature for NI whereas nπ* character predominates for the NDI. This difference exerts a profound effect on subsequent reaction mechanisms: upon irradiation, only the NDI molecules can undergo intramolecular γ hydrogen abstraction. In the case of NP-III, a bishydroperoxy NDI derivative, this photoprocess (Φ = 0.03) leads to concomitant formation of an oxygen-centered radical (e = 21 600 M-1 cm-1 at 465 nm in acetonitrile) and release of the hydroxyl radical (•OH). All the compounds studied produce the triplet state (in acetonitrile, eT ≈ 10 500−11 ...
Published Version
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