O-Acyloxime Photobased: Photochemical Properties, Triplet Sensitization and Efficiency of Base Formation

The influence of the molecular structure ana the required conditions for triplet state bond breaking of carefully selected 0-acyloximes usable as photobase generators are deeply investigated. A clear non vertical character in triplet-triplet energy transfer was found in compounds exhibiting a flexible aryl- CN-O- moiety. This effect strongly affects the triplet sensitized decomposition process, due to the; possible formation of a non-relaxed excited triplet state from which dissociation can occur. All these facts were rationalized in a mechanism which well explain the results of the photoinitiated thermal crosslinking of suitable resins carried out in model media.