Influence of structure of benzodioxole derivatives on photoinitiation efficiency of benzophenone

To investigate the influence of the substituents at the 5-position of the phenyl ring of benzodioxole on the reactivity of a benzophenone (BP)/benzodioxole-based photoinitiator system, three benzodioxole-based compounds were synthesized in this study. The structure was characterized by FT-IR, H-1 NMR and C-13 NMR. The kinetics were monitored by a real-time Fourier Transform near-IR (FT-NIR) spectrometer. The results showed that the introduction of the electron-donating substituents in the 5-position of the phenyl ring contributed to the increase in the reactivity of the BP/benzodioxole-based system. On the contrary, the electron-drawn substituents at the 5-position of the phenyl ring caused the opposite effect. Compared with the BP/ethyldimethylaminobenzoate (EDAB) photoinitiating system, the combination of BP/5-methoxy-1,3-benzodioxole (BDOOMe) led to almost the same R-pmax and final double bond conversions. It indicated that BDOOMe had the potential to be used as a coinitiator in the place of an amine in current BP/amine initiating systems for practical applications to decrease cytotoxicity and yellowing.