Photoswitching of 5-phenylazopyrimidines in crystalline powders and thin films

• Published in: Dyes and pigments 2022-03, Vol.199, p.110066, Article 110066
• Main Authors: Procházková, Eliška, Filo, Juraj, Čechová, Lucie Mužíková, Dračínský, Martin, Císařová, Ivana, Janeba, Zlatko, Kawamura, Izuru, Naito, Akira, Kuběna, Ivo, Nádaždy, Peter, Šiffalovič, Peter, Cigáň, Marek
• Format: Article
• Language: English
• Subjects: Azo dyes; NMR spectroscopy; Solid-state photoswitching; Thin films
• ISSN: 0143-7208; 1873-3743
• DOI: 10.1016/j.dyepig.2021.110066

Solid-state photoswitching enables the development of smart materials. However, the close packing of molecules and the lack of free volume in this state prevent sterically demanding structural changes induced by irradiation, thereby precluding the use of azobenzene photoswitches. Nevertheless, we report here the solid-state photoswitching of their derivatives, 5-phenylazopyrimidines, in crystalline powders and in amorphous thin layers. After identifying trans-cis photoisomerization by NMR spectroscopy, we demonstrated the applicability of 5-phenylazopyrimidines for future all-optical switching applications. For this purpose, we prepared thin films by spin-coating and confirmed their solid-state optical switching by optical transmission spectroscopy and their favorable surface topography by atomic force microscopy. Therefore, thin films of 5-phenylazopyrimidines are suitable for on-chip integration for emerging all-optical technologies. [Display omitted] •Azopyrimidine photoswitching in solid state is led by trans-to-cis photoisomerization.•Photoisomerization efficiency differs in crystalline powders and amorphous thin films.•Thin films show suitable properties for on-chip integration in all-optical technology.