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Updated: Dec 10, 2025

Determination of the Photoisomerization Quantum Yield of a Hydrazone Photoswitch
Published on: February 7, 2022
New azobenzene liquid crystal with dihydropyrazole heterocycle and photoisomerization studies
Xiaoxuan Wang1, Zhaoxia Li1, Haiying Zhao1
1Inner Mongolia Key Laboratory of Fine Organic Synthesis, College of Chemistry and Chemical Engineering, Inner Mongolia University, Hohhot 010021, People's Republic of China.
Abstract:
New azobenzene derivatives with dihydropyrazole heterocycle have been prepared and characterized. According to thermal polarizing microscopy and differential scanning calorimetry studies, the compounds consisting of four linearly linked rings and a long alkoxy chain on the azobenzene side (3a-8 and 3a-14) displayed no liquid crystal properties. When the length of mesogenic unit increased to five rings, except for compound 5a-8, all compounds from 5a-10 to 5a-16 containing a long chain of 10-16 carbon atoms on the side of ester group displayed liquid crystalline properties, and the mesogenic domain gradually narrowed with increase of the chain length. However, in the case of the molecule with long alkoxy chains on both sides, only 5c-16 with a long chain of 16 carbon atoms exhibited liquid crystal behaviour. In addition, these azo compounds underwent isomerization from E to Z under ultraviolet irradiation and then thermal back relaxation slowly in the dark, which can be recycled many times.
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