Photochromism of a pyrazolone derivative in crystalline state and in HPMC composite film.

A novel photochromic compound, 1,3-diphenyl-4-(3-chloro-4-fluorobenzal)-5-hydoxypyrazole 4-phenylsemicarbazide (1a), has been synthesized by introducing a phenylsemicarbazide unit. The material exhibits good fatigue resistance and reversible fluorescent switching properties with distinct fluorescence on/off ratio under alternating UV irradiation and heating at 120 °C. For the fabrication of actual application materials, 1a/hydroxypropylmethylcellulose (HPMC) composite film has been successfully fabricated using hydrogel casting method. The 1a/HPMC composite film obtained can also show reversible photochromic reaction under UV irradiation and rapid thermal bleaching properties by heating. The HPMC composite film shows similar good photochromic properties as those of 1 in the crystalline state.