Research Center for Solar Energy Chemistry, and Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University, Toyonaka 560-8531, Japan.
Phys Chem Chem Phys. 2010 Nov 7;12(41):13737-45. doi: 10.1039/c0cp00140f. Epub 2010 Sep 28.
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 SP → MC 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 SP → MC 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.
已研究了在水介质中螺吡喃衍生物的热致顺反异构化。无色螺环（SP）形式的螺吡喃衍生物即使在黑暗条件下，在高温下也会异构化为有色的硫代色烯（MC）形式。平衡、动力学和氘实验表明，热 SP→MC 异构化是由于 MC 形式通过与水分子的氢键相互作用而稳定化。这导致 MC 形式的基态能量降低到低于 SP 形式，从而导致 SP→MC 异构化。这种热异构化性质可用于粗略指示溶液温度。螺吡喃衍生物在适当光强度的可见光照射下溶解在水介质中时，随着温度的升高，MC 吸收增加。无论加热/冷却顺序如何，吸收响应都是可逆的。因此，螺吡喃衍生物具有比色温度指示的潜力。
