A family of azoquinoline derivatives: Effect of the substituent at azo linkage on thermal cis-trans isomerization based on an experimental and computational approach. (April 2020)

• Record Type: Journal Article
• Authors: Bujak, Karolina; Wasiak, Anna; Sobolewska, Anna; Bartkiewicz, Stanislaw; Malecki, Jan G.; Nycz, Jacek E.; Schab-Balcerzak, Ewa; Konieczkowska, Jolanta
• Is Part Of: Dyes and pigments. Volume 175(2020)
• Publication Date: 2020-04
• Subjects: Azoquinoline -- Photoisomerization reaction -- cis-trans thermal relaxation -- DFT calculations; Dyes and dyeing -- Periodicals; Pigments -- Periodicals; 667.2
• DOI: 10.1016/j.dyepig.2019.108151
• Languages: English
• ISSNs: 0143-7208

Abstract

Abstract: The subject of the research is a series of azo-dyes based on the quinoline structure, which are practically omitted as materials which use photoinduced optical anisotropy for applications. The work presents the kinetics of thermal cis-trans isomerization reaction of 5-azo-8-hydroxy-2-methylquinoline and 5, 5'-((1 E, 1′ E )-[1, 1′-biphenyl]-4, 4′-diylbis(diazene-2, 1-diyl))bis(2-methylquinolin-8-ol) compounds. The impact of the structure of the substituent at the azo linkage on the cis-trans isomerization kinetics was investigated experimentally and theoretically using the UV–Vis spectroscopy and the density-functional theory (DFT). The kinetics of the dark-return of the cis- to trans -isomer of azoquinolines was investigated after UV-irradiation. It was found that attaching the nitro substituent to the azoquinolines structure retards the photoisomerization process in comparison to the other substituents (i.e. F, Cl, Br, N atoms or CH3, OH, COOH, OCH3 groups). The calculated rate constants were in qualitative agreement with the experimental values. To the best of our knowledge, the cis-trans isomerization kinetics for azoquinolines has not been studied yet. Graphical abstract: Image 1 Highlights: The cis-trans isomerization kinetic of azoquinoline derivatives was investigated. The nitro-substituted azodyes exhibit the fastest isomerization (kc-t > 1.9 s −1 ). The rotation-assisted inversion character of the cis-trans isomerization was showed. An increase of the kc-t rate constant caused a decrease in the efficiency of the cis-trans reaction.