Synthesis and spectroscopic properties of novel cinnamate derivatives of thioxanthone: photocuring activity versus photodimerization

摘要: Abstract Two novel 2-substituted derivatives of thioxanthone-containing cinnamate (ethyl ester 2-propenoic acid) and cinnamamide ( N , -dimethylacrylamide) groups are synthesized characterized. The spectroscopic properties these two new photoinitiators examined related to their photocuring behaviour in an epoxy acrylate resin compared with those commercial 2-isopropylthioxanthone. Despite increase the longest wavelength absorption maximum corresponding extinction coefficient, most showed little improvement activity when Their lower activities were reflected reduced fluorescence quantum yields phosphorescence yields. Photolysis esters, however, found be increased In this case photoreaction was observed both nitrogen-saturated oxygen-saturated 2-propanol. Using FT i.r. n.m.r. analysis, undergo a primary reaction involving (2 + 2) cycloaddition via lowest excited singlet state. is compete effectively hydrogen atom abstraction. This confirmed on microsecond flash photolysis by absence any ketyl radical formation role controlling photochemical thioxanthone chromophore discussed.