Structure and isomerization behavior relationships of new push-pull azo-pyrrole photoswitches

• Published in: Organic & biomolecular chemistry 2024-05, Vol.22 (2), p.4123-4134
• Main Authors: Gallardo-Rosas, D, Guevara-Vela, J. M, Rocha-Rinza, T, Toscano, R. A, López-Cortés, J. G, Ortega-Alfaro, M. C
• Format: Article
• Language: English
• Subjects: Absorption spectra; Azo compounds; Chemical reactions; Doppler effect; Irradiation; Isomerization; Optical properties; Red shift; Spectrophotometry; White light
• ISSN: 1477-0520; 1477-0539
• DOI: 10.1039/d4ob00417e

A family of stilbenyl-azopyrroles compounds 2a-d and 3a-d was efficiently obtained via a Mizoroki-Heck C-C-type coupling reaction between 2-(4′-iodophenyl-azo)- N -methyl pyrrole ( 1a ) and different vinyl precursors. The influence of the π-conjugated backbone and the effect of the pyrrole moiety were correlated with their optical properties. Studies via UV-Visible spectrophotometry revealed that the inclusion of EWG or EDG favors a red-shift of the main absorption band in these azo compounds compared with their non-substituted analogues. Furthermore, there is a clear influence between the half-life of the Z isomer formed by irradiation with white light and the push-pull behavior of the molecules. In several cases, the stilbenyl-azopyrroles led to the formation of J-type aggregates in binary MeOH : H 2 O solvents, which are of interest for water compatible applications. Push-pull stilbenyl-azopyrrole dyes are efficiently obtained via a Heck cross-coupling reaction. Modifications of the acceptor character of the EWG might accelerate the cis - trans photo-isomerization.