Photochemistry of thioxanthones. IV: spectroscopic and flash photolysis study on novel n-propoxy and methyl n-propoxy derivatives

摘要: The spectroscopic properties of seven oil soluble n-propoxy and methyl, substituted thioxanthone structures have been examined in various solvents the data compared to their photopolymerization efficiencies, photochemical stabilities flash photolysis behaviours solution. Absorption maxima, extinction coefficients, fluorescence phosphorescence spectra quantum yields measured. Generally, all compounds exhibit low high but ratio is solvent dependent. These observations are consistent with photoreactivity molecules operating lowest excited triplet state which nπ* character. Photopolymerization rates n-butyl methacrylate N-diethylmethylamine co-initiator correlate absorption maxima coefficients thioxanthones also degree quenching by amine, indicating importance electron transfer. In absence a tertiary transient formation on micro-second 2-propanol associated ketyl radical formed abstracting hydrogen atom from solvent. presence both anion (at longer wavelengths) observed, latter being via abstraction an amine. This confirmed study using amines ionization potentials where correlation observed absorbance. A pH confirms identity species. Activation molecule 3 4 positions methyl group enhances initiator activity whereas substitution t-position deactivates through intra-molecular abstraction.