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Issue 8, 2020
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π-Extended push–pull azo-pyrrole photoswitches: synthesis, solvatochromism and optical band gaps

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Abstract

A new family of push–pull biphenyl-azopyrrole compounds 3b–g and 4b–d was efficiently obtained via a Suzuki cross-coupling reaction between 2-(4′-iodophenyl-azo)-N-methyl pyrrole (1a) or 3-(4′-iodophenyl-azo)-1,2,5-trimethyl pyrrole (2a) and 4′-substituted phenyl boronic acids in excellent yields. The influence of the π-biphenyl backbone and pyrrole pattern substitution was correlated with their optical properties. Solvatochromic studies via UV-visible spectrophotometry revealed that the inclusion of a 4′-nitro-biphenyl fragment favors a red-shift of the main absorption band in these azo compounds compared with their non-substituted analogues. Likewise, optical band-gaps were estimated by means of electronic absorption spectra and correlated with TD-DFT studies. The pyrrole pattern substitution and the π-conjugated backbone exhibit a clear influence on their thermal isomerization kinetics at room temperature. In all cases, biphenylazo-pyrrole compounds lead to the formation of J-type aggregates in binary MeOH : H2O solvents. Under these conditions, compounds 3b–c undergo a water-assisted cis-to-trans isomerization at room temperature.

Graphical abstract: π-Extended push–pull azo-pyrrole photoswitches: synthesis, solvatochromism and optical band gaps

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Supplementary files

Article information


Submitted
07 Nov 2019
Accepted
03 Feb 2020
First published
03 Feb 2020

Org. Biomol. Chem., 2020,18, 1657-1670
Article type
Paper

π-Extended push–pull azo-pyrrole photoswitches: synthesis, solvatochromism and optical band gaps

J. A. Balam-Villarreal, B. J. López-Mayorga, D. Gallardo-Rosas, R. A. Toscano, M. P. Carreón-Castro, V. A. Basiuk, F. Cortés-Guzmán, J. G. López-Cortés and M. C. Ortega-Alfaro, Org. Biomol. Chem., 2020, 18, 1657
DOI: 10.1039/C9OB02410G

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