Bichromophoric dye derived from benzo[1,3]oxazine system

The reaction of 2-methylbenzo[1,3]oxazine with julolidine-9-carbaldehyde under acid catalysis afforded an highly coloured blue dye with an intense absorption at 591 nm. NMR and UV–Vis analysis showed that this compound has an opened oxazine structure with a polymethine-type chromophore, corresponding to a protonated thermally stable coloured form of photochromic benzo[1,3]oxazines that are known to be unstable at room temperature with lifetimes in the ns timescale. In basic medium this dye is converted into a stable opened zwitterionic form of photochromic benzo[1,3]oxazines with two absorption maxima at 410 and 587 nm assigned to conjugated 3H-indolium and 4-nitrophenolate chromophores respectively.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Synthesis of a stable open form of photochromic benzo[1,3]oxazines. ► Synthesis of a thermally stable zwitterionic dye with two chromophores. ► Reversible acidochromic behaviour.