Experimental and Theoretical Characterization of Ultrafast Water-Soluble Photochromic Photoacids
| Autor: | Nicholas A. Miller, Nawodi Abeyrathna, Yi Liao, Paul M. Zimmerman, Roseanne J. Sension, Theodore E. Wiley, Cody R. Aldaz |
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| Rok vydání: | 2021 |
| Předmět: |
Spiropyran
010304 chemical physics 010402 general chemistry Photochemistry 01 natural sciences 0104 chemical sciences Surfaces Coatings and Films chemistry.chemical_compound Photochromism Deprotonation chemistry Solvent models 0103 physical sciences Ultrafast laser spectroscopy Materials Chemistry Merocyanine Physical and Theoretical Chemistry Spectroscopy Isomerization |
| Zdroj: | The Journal of Physical Chemistry B. 125:4120-4131 |
| ISSN: | 1520-5207 1520-6106 |
| DOI: | 10.1021/acs.jpcb.1c00644 |
| Popis: | UV-visible transient absorption spectroscopy and quantum mechanical simulations are combined to elucidate the photochemical mechanism of two metastable merocyanine/spiropyran photoacids, 2-[(E)-2-(2-hydroxyphenyl)ethenyl]-3,3-dimethyl-1-(3-sulfopropyl)-3H-indol-1-ium (phenylhydroxy-MCH) and 2-[(E)-2-(1H-indazol-7-yl)ethenyl]-3-(3-sulfopropyl)-1,3-benzothiazol-3-ium (indazole-MCH). Transient absorption spectra demonstrate that trans-acid isomerization to the cis form results in deprotonation on a picosecond time scale. Ring closure to form spiropyran follows promptly from the appropriate conformation or follows at longer time delays (≫3.5 ns) following a barrier crossing for single-bond isomerization to the appropriate conformation. Consistent with the results of Berton et al. [ Chem. Sci. 2020, 11, 8457-8468] , we find that cis-phenylhydroxy-MCH is a stronger acid than trans-phenylhydroxy-MCH. The decrease in pKa upon isomerization is further investigated to benchmark quantum chemical methods for their accuracy. Calculations were performed with nine levels of theory including continuum solvent models and explicit water. The calculations are not sufficient to describe the ΔpKa following isomerization of these photoacids, and more work is necessary to properly evaluate the physical basis for the acidity of the cis photoacids. |
| Databáze: | OpenAIRE |
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