Benzophenone based salicylaldimine and its boron complex as radical photoinitiator: A comparative study

Salicylaldimine derivatives are photochromatic dyes which could be easily synthesized from aromatic amine and salicylaldehyde. However, those compounds were rarely reported as photoinitiator. In this work, a salicylaldimine containing benzophenone moiety (BPH), and its boron complex (BPB) were synthesized and carried out as radical photoinitiator under 365/405 nm LED lamps. BPB was never synthesized before. Photopolymerization results indicate that BPB presented better initiation performance than that of BPH. Photolysis experiments showed that BPB reacted faster with co-initiator triethanolamine. The photophysical property and redox potential of BPH and BPB were characterized by using various technique to understand their diverse performance. Results showed that BPB displayed typical triplet absorption of benzophenone, which was not observed in BPH. In addition, BPB presented higher reduction potential, which is also beneficial to its reaction with co-initiator.