Photochemistry of thioxanthones—III. Spectroscopic and flash photolysis study on hydroxy and methoxy derivatives

摘要: Abstract The spectroscopic properties of 9 oil soluble hydroxy and methoxy thioxanthone derivatives have been examined in various solvents the data compared to their photopolymerization efficiency flash photolysis behaviour solution. Absorption maxima, extinction coefficients, fluorescence phosphorescence spectra quantum yields measured. Generally, most compounds exhibit low high except 1-substituted where intra-molecular hydrogen bonding is involved. These observations are consistent with photoreactivity molecules occurring via lowest excited triplet state. Photopolymerization rates n-butyl methacrylate, using N-diethylmethylamine as co-initiator, correlate some extent absorption maxima coefficients thioxanthones. Transient formation on micro-second associated ketyl radical formed by state thioxanthones abstracting a atom from solvent. In presence tertiary amine, new longer wavelength transient produced assigned radical-anion an electron amine. A correlation was observed between due ionisation potential amines. Flash studies acid base media confirmed identity radical-ion species. Intra-molecular α-position carbonyl group deactivates both singlet states but has little effect polymerization efficiency. latter competition amine co-initiator for consequent abstraction give active radical-anion. This photolysis.