title: Synthesis and improved photochromic properties of pyrazolones in the solid state by incorporation of halogen.
abstract: Four novel photochromic pyrazolones have been prepared by introducing halogen atoms as substituents on the benzene ring. All as-synthesized compounds exhibited excellent reversible photochromic performances in the solid state. Upon UV light irradiation, the as-synthesized compounds can change their structures from E-form to K-form with yellow coloration. Further processed by heating, they rapidly reverted to their initial states at 120°С. Their photo-response and thermal bleaching kinetics were detailed investigated by UV absorption spectra. The results showed that the time constants were higher than that of our previously reported compounds at least one order of magnitude and the rate constants of the as-synthesized compounds were significantly influenced by the size and electronegativity of different halogen atoms. The fluorescence emission were modulated in a high degree via photoisomerization of pyrazolones, which might be due to the efficient energy transfer from E-form to K-form isomers for their partly overlaps between their E-form absorption spectra and K-form fluorescence spectra.
authors: Key Laboratory of Energy Materials Chemistry, Ministry of Education, Xinjiang University, Urumqi 830046, Xinjiang, PR China; Institute of Applied Chemistry, Xinjiang University, Urumqi 830046, Xinjiang, PR China; Key Laboratory of Advanced Functional Materials, Autonomous Region, Xinjiang University, Urumqi 830046, Xinjiang, PR China.
authors: Jixi
authors: J
authors: Guo
authors: Key Laboratory of Energy Materials Chemistry, Ministry of Education, Xinjiang University, Urumqi 830046, Xinjiang, PR China; Institute of Applied Chemistry, Xinjiang University, Urumqi 830046, Xinjiang, PR China; Key Laboratory of Advanced Functional Materials, Autonomous Region, Xinjiang University, Urumqi 830046, Xinjiang, PR China.
authors: Hui
authors: H
authors: Yuan
authors: Key Laboratory of Energy Materials Chemistry, Ministry of Education, Xinjiang University, Urumqi 830046, Xinjiang, PR China; Institute of Applied Chemistry, Xinjiang University, Urumqi 830046, Xinjiang, PR China; Key Laboratory of Advanced Functional Materials, Autonomous Region, Xinjiang University, Urumqi 830046, Xinjiang, PR China. Electronic address: jdz0991@gmail.com.
authors: Dianzeng
authors: D
authors: Jia
authors: Key Laboratory of Energy Materials Chemistry, Ministry of Education, Xinjiang University, Urumqi 830046, Xinjiang, PR China; Institute of Applied Chemistry, Xinjiang University, Urumqi 830046, Xinjiang, PR China; Key Laboratory of Advanced Functional Materials, Autonomous Region, Xinjiang University, Urumqi 830046, Xinjiang, PR China.
authors: Mingxi
authors: M
authors: Guo
authors: Key Laboratory of Energy Materials Chemistry, Ministry of Education, Xinjiang University, Urumqi 830046, Xinjiang, PR China; Institute of Applied Chemistry, Xinjiang University, Urumqi 830046, Xinjiang, PR China; Key Laboratory of Advanced Functional Materials, Autonomous Region, Xinjiang University, Urumqi 830046, Xinjiang, PR China.
authors: Yinhua
authors: Y
authors: Li
keywords: Fluorescence switch; Photochromism; Proton transfer; Pyrazolones