Solid-state photochromism of pyrazolones with highly improved sensitivity, fatigue resistance and reversible fluorescent switching properties

Photochromic compounds derived from pyrazolones, which undergo reversible photoisomerization reactions in pure solid state, were synthesized toward the end of designing novel solid-state photonic switches. The materials exhibit high sensitivity, excellent fatigue resistance and reversible fluorescent switching properties with distinguishable contrast signals under alternating UV irradiation and heating. The mechanism of the photochromic reactions was verified by FT-IR and XPS. The detailed analysis of the spectra and crystal structure of the materials revealed that their photochromism resulted from tautomerization between their enol and keto forms accompanied by proton transfer.