Synthesis and Photochemistry of Tertiary Amine Photobase Generators

A family of tertiary amine photobase generators have been prepared and studied. The compounds investigated were quaternary ammonium salts of benzhydrylamine (aminodiphenylmethane) and 9-aminofluorene. The compounds were prepared by the following methods: methylation of the benzhydryl or fluorenylamines, reaction of a tertiary amine with 9-bromofluorene, and reaction of a primary or secondary amine with 9-bromofluorene followed by exhaustive methylation. Alkylation was limited to methylation in the benzhydryl system, as larger alkyl groups would not react. This appears to be a result of steric hindrance. The fluorenyl system allowed for a wider variation in the synthesis of tertiary amine photobase generators. Examination of the solution photochemistry by NMR spectroscopy supported a heterolytic mechanism for photodecomposition.