The photoswitching properties of two easily synthesized isatin 4-nitrophenylhydrazones were investigated. Although the parent isatin 4-nitrophenylhydrazones exhibit low addressability which hampers their photochromic applications, the addition of strongly basic anions to phenylhydrazone solutions creates a new Vis-Vis photochromic system with the unusual azo/azine-to-hydrazone photo-tautomerization process as the photoswitching mechanism. To the best of our knowledge, this is the first report related to the anion-assisted azo/azine-to-hydrazone photo-tautomerism.
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