New azobenzene liquid crystal with dihydropyrazole heterocycle and photoisomerization studies

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.

Azobenzene isomerization in condensed matter: lessons for the design of efficient light-responsive soft-matter systems

“…For this reason, it is simpler to here compare UV-visible spectra to look for H-aggregation rather than only looking for studies on isomerization efficiency, however, care should be taken because often it is only a dilute solution-state absorbance spectrum of the azobenzene chromophore that is reported. 103,[126][127][128] UV-visible spectra of films of azobenzene-containing liquid crystals, where the azobenzene component is the main constituent, 129 where it is a minor dopant 130,131 and liquid crystal polymers, 132 often display spectral shifts in the p to p* excitation that are consistent with those observed for partially diluted SAMs. 92 The extent of hypsochromic shifting observed appear to trend as expected, with greater aggregate formation arising from increases in azobenzene content.…”

Cellulose Ether-Based Liquid Crystal Materials: Review Article

“…Some heterocyclic compounds and detergents can form LC mesophases [37,38]. Besides low molecular weight LC, there are lots of polymer substances that exhibit liquid crystalline behavior [25,26].…”

Catalytic synthesis of azoarenes via metal-mediated nitrene coupling

“…13,14 Azobenzene-based photoswitches are used in many applications including polymers, biomolecules, lightgated glutamate receptors (MAG), photoactive Brønsted bases, energy storage materials, and liquid crystals. [15][16][17][18][19][20][21][22][23][24][25][26] Additionally, azobenzene derivatives such as Congo Red and Sulfasalazine have been used for various biomedical applications. 27 Selected examples of azoarene derivatives are provided in Fig.…”