ABSTRACT
Five photochromic terarylenes which show reversible photocyclisation and cycloreversion with relatively high quantum yields are presented. Some of these have been observed to undergo a highly efficient cycloreversion cascade process from their coloured, closed forms to their uncoloured open forms that leads to cycloreversion quantum yields significantly larger than unity. This cascade effect can been induced with both chemical and X-ray initiation; the limit of detection from X-ray initiation has been tested and is comparable to existing systems with detection observed at values as low as 0.3 mGy.
ABSTRACT
We present here a new photo-active molecule which acts as a photo-Lewis acid generator (PLAG) based on photo-chemical 6π-percyclization. Photo-illumination of the PLAG molecule produces a condensed aromatic carbocation with a triflate counteranion, which exhibits Lewis acid chemical catalytic reactivity such as initiation of the polymerization of epoxy monomers and catalysis of Mukaiyama-aldol reactions. The terminal-end structure in the epoxy polymerization was modified with the Lewis acid fragment. The carbocation induced the Mukaiyama-aldol reaction as a new photo-gated system with remarkably high catalytic reactivity and turnover numbers higher than 60. The photo-chemical quantum yield of the carbocation generation is 50%, which is considerably higher than obtained with most Brønsted photo-acid generators.
