ORGANIC PHOTOCHROMIC COMPOUND

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Organic photochromic compounds which have different kinds of transformation mechanism are brought up for the studies of optical properties and photoreaction in solid form : furylfulgide (electrocyclization), azobenzene (E-Z isomerization and N-salicylideneaniline (hydrogen transfer). The conditions of crystal growth are found. Polarized reflection spectra of the single crystals are measured for wide energy range from 1 to 30 eV,and results are transformed to absorption spectra by the K-K relation. The spectra are well understood by the energy diagram of single molecule (pi-pi* transition), though the spectra are shift to the lower energy a little by forming Frenkel excitons in the crystal.A try of material control by light, using single crystals of the photochromic compounds is done successfully. A film of the isomer on the fulgide crystal surface is grown by irradiation of the light with large absorption coefficient. The film has absorption only for the light polarized parallel to the b axis of the crystal, showing that the films are well oriented. Optical doping in to the crystal by light is also done by irradiation of the light with small absorption coefficient. An absorption band by the photoproduced material shows blue shift with increasing the amounts of the produced material for the film, on the other hand, red shift for the photodoped materials which are dilute in density compared with the surface film. All the photoproduced material on the surface or inside of the crystal was able to be erased by the irradiation of the visible light.Furylfulgides with different sizes of alkyl substitituents were synthesized and their photochromic properties of the quantum yield of coloration, bleaching quantum yeild and the change of the absorption spectra were examined.