Many derivatives of 1,3,3-trimethylspiro[indoline-2,2′-benzopyran] (1) exhibit photoreversible color changes in organic solvents. One of the derivatives 1,3,3-trimethylspiro[indoline-2,2′-benzopyran]-8′-carboxylic acid (2) shows “reverse photochromism” in polar solvents. The compound 2 exhibits a deep color in the polar solvent and the color is bleached by irradiation with either visible or ultraviolet light. The color reappears thermally as the irradiation is ceased. The thermal conversion rate from the colorless form to the colored one depends on the solvents. On the other hand, the isomer 1,3,3-trimethylspiro[indoline-2,2′-benzopyran]-6′-carboxylic acid shows neither normal nor reverse photochromism under usual conditions, but exhibits reverse photochromism when acid such as malonic acid is added into the solution. The compound 2 is assumed to have a merocyanine dye-like structure due to the intramolecular proton transfer.

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Alcohols have been shown to be useful as oxidizing agents of diethylzinc for the growth of ZnO films by MOCVD. C-axis oriented ZnO films have been deposited on glass substrates at 300°C. The problem of a premature reaction, which is observed between diethylzinc and oxygen or water vapor, is shown to be overcome when alcohols are used instead. The formation, stability and decomposition of the precursor of MOCVD, e.g., adducts, are discussed on the basis of a mass-spectroscopy analysis.

1,3,3-Trimethylindolino-6′-nitro-benzopyrylspiran (1) exhibits a photoreversible color change which is called “photochromism”. However, it is transformed from a colorless form (A) into a colored form (C) which has a salt-like structure when acid such as malonic acid is added into acetone without irradiation with light. The color is bleached by irradiation with light. The color reappears thermally as the light source is removed. This photoreversible color change is termed “reverse photochromism”. Another colored form (B) of compound (1) which has a merocyanine dye-like structure is converted into (C) as acid is added into the solution (B). The quantum yield of the photoconversion from C to A by irradiation with visible light depends on the solvent polarity. The quantum yield of the photoconversion from A to B also depends on the solvent polarity.

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