Photoinduced Intramolecular Electron Transfer between Carbazole and Bis(trichloromethyl)-<i>s</i>-triazine Generating Radicals

Abstract

An intramolecular electron transfer and photosensitivity in dye/initiator systems, in which an electron donating light-absorbing unit (carbazole) is tethered by methylene bonds to an electron-deficient initiator [bis(trichloromethyl)- s -triazine], was investigated. The efficient quenching of fluorescence was observed in the tethered compounds in a rigid matrix at low temperature, and the higher sensitivity of photopolymerization was observed in the photopolymer films containing the tethered compounds as photoinitiating systems compared with the films containing physical mixtures of dye and initiator. The compounds tethered by a longer methylene chain (C6 and C11) showed a higher photosensitivity than that tethered by a shorter methylene chain (C2 and C3), despite the efficient fluorescence quenching in the latter compounds. Control of back electron transfer after initial electron transfer or control of radiationless deactivation via exciplex formation was suggested to be important factor to design efficient dye-linked photoinitiators.