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Issue 41, 2010
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Thermal isomerization of spiropyran to merocyanine in aqueous media and its application to colorimetric temperature indication

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Abstract

Thermally-induced isomerization of spiropyran derivatives in aqueous media has been studied. The colorless spirocyclic (SP) forms of spiropyran derivatives are isomerized to colored merocyanine (MC) forms even in dark conditions at elevated temperature. Equilibrium, kinetic, and deuterium experiments reveal that the thermal SPMC isomerization is due to the stabilization of MC form by a hydrogen bonding interaction with water molecules. This leads to the ground state energy of the MC form decreasing to lower than that of the SP form, resulting in SPMC isomerization. The thermal isomerization property is applicable to a rough indication of solution temperature. The spiropyran derivatives, when dissolved in aqueous media under irradiation of visible light with an appropriate light intensity, demonstrate an increase in MC absorbance with a rise in temperature. The absorption response occurs reversibly regardless of the heating/cooling sequence. The spiropyran derivatives therefore have a potential for colorimetric temperature indication.

Graphical abstract: Thermal isomerization of spiropyran to merocyanine in aqueous media and its application to colorimetric temperature indication

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Publication details

The article was received on 06 Apr 2010, accepted on 28 Jul 2010 and first published on 28 Sep 2010


Article type: Paper
DOI: 10.1039/C0CP00140F
Citation: Phys. Chem. Chem. Phys., 2010,12, 13737-13745
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    Thermal isomerization of spiropyran to merocyanine in aqueous media and its application to colorimetric temperature indication

    Y. Shiraishi, M. Itoh and T. Hirai, Phys. Chem. Chem. Phys., 2010, 12, 13737
    DOI: 10.1039/C0CP00140F

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