ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 38, Number 12
JKCSEZ 38(12)
December 20, 1994 

Absorption spectra of thermochromic spiropyran and spirooxazine derivatives were investigated. The effects of solvent polarity on the absorption spectra indicate that the merocyanine-like form of non-substituted spiro compound is likely to the quinoid type. However, the merocyanine-like form of electron-withdrawing substituted spiro compound is likely to the zwitter-ion type. The enthalpy changes between the closed and merocyanine-like forms were measured. The enthalpy change of spiro compound decreases as the solvent polarity increases. The UV-Vis spectrum of merocyanine-like form was resolved into three Lorentzian-Gaussian product bands. The solvent dependence of the amount of the three band was also examined.