Journal
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
Volume 13, Issue 16, Pages 7322-7329Publisher
ROYAL SOC CHEMISTRY
DOI: 10.1039/c0cp01989e
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Funding
- KAKENHI [20350110]
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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 60- or 80-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 80-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.
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