Photochromism of Heterocyclic Fulgides. IV. Relationship between Chemical Structure and Photochromic Performance

The absorption spectra and quantum yields of various heterocyclic fulgides were measured. The absorption maxima of the colored photocyclization products of fulgides were dependant upon the structure of heterocyclic rings and the substituent; and increase of the electron-donating ability of the heterocyclic ring caused a red shift of λmax. A quantum yield measurement of the photochromic reaction of fulgides revealed that not only the steric effect, but also the electronic effect of substituent (e.g. p-(dimethylamino)phenyl, cyano, acetyl) introduced into the heterocycles, changed the reactivity for both coloration and bleaching.