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Issue 16, 2011
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Isomerization of spirobenzopyrans bearing electron-donating and electron-withdrawing groups in acidic aqueous solutions

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Abstract

Spirobenzopyrans, which are well known as photochromic compounds, exist as thermodynamically stable protonated ring-opened isomers (protonated merocyanine form, McH) in an acidic aqueous solution in the dark. In the present study, we investigated effects of substitution of the spirobenzopyrans on a ring-opening behavior in an aqueous system. We prepared five polymerizable spirobenzopyrans that are substituted with a methoxy group or a nitro group at the 6′- or 8′-positions and without a substituent. These monomers were copolymerized with N,N-dimethylacrylamide to evaluate the spirobenzopyrans in aqueous solution. Correlation between ring-opening rates and the kind and position of the substitution can be summarized as follows: the substitution of an electron-donating methoxy group and the substitution at the 8′-position increased the ring-opening rate, whereas the substitution of an electron-withdrawing nitro group decreased the rate. The effects of the substitution can be explained by changes in the electron density of the oxygen atom of the spirobenzopyrans.

Graphical abstract: Isomerization of spirobenzopyrans bearing electron-donating and electron-withdrawing groups in acidic aqueous solutions

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Publication details

The article was received on 01 Oct 2010, accepted on 10 Feb 2011 and first published on 11 Mar 2011


Article type: Paper
DOI: 10.1039/C0CP01989E
Citation: Phys. Chem. Chem. Phys., 2011,13, 7322-7329
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    Isomerization of spirobenzopyrans bearing electron-donating and electron-withdrawing groups in acidic aqueous solutions

    T. Satoh, K. Sumaru, T. Takagi, K. Takai and T. Kanamori, Phys. Chem. Chem. Phys., 2011, 13, 7322
    DOI: 10.1039/C0CP01989E

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