Tadatsugu Yamaguchi

Substituent effect on the photochromic reactivity of bis(2-thienyl)perfluorocyclopentenes

Abstract Substituent effect on the photochromic reactivity of bis(2-thienyl)perfluorocyclopentenes was examined. Introduction of phenyl groups having electron-donating substituents on the para -position of the phenyl ring to the 5-position of the thiophene rings shifted the absorption bands of the open-ring isomers to longer wavelengths and reduced the quantum yield of the cyclization reactions. The substitution with p -( N , N -diethylamino)phenyl groups prohibited the cyclization reaction. The absorption spectra of the closed-ring isomers were not influenced by the substitution.

Photoinduced pitch changes in chiral nematic liquid crystals formed by doping with chiral diarylethene

Chiral binaphthyl derivatives having two photochromic diarylethene units were synthesized in an attempt to use them as dopants for photoresponsive liquid crystals. These compounds showed thermally irreversible photochromic reactions. The circular dichroism (CD) spectra and the optical rotation values of the derivatives reversibly changed in methanol upon alternate irradiation with ultraviolet and visible light. Large photostimulated pitch changes of chiral nematic K-15 liquid crystals were observed on addition of the derivatives as dopants. The relation between the optical rotation and the twisting power force was discussed.

Photochromic and fluorescent properties of bisfurylethene derivatives

Photochromic diarylethenes having furan units (1 and 3) were synthesized and their photochromic performances were compared with those having thiophene units. The cyclization quantum yields of both derivatives in hexane are similar. In contrast, the cycloreversion quantum yield of the derivative having furan units (1) is much larger than that having thiophene units (2) in hexane. The difference is attributed to the conformation of the closed-ring isomers. Although 2a and 4a do not show any fluorescence, 1a and 3a exhibit fluorescence. Photochromism in the single crystalline phase was also observed for 1 and 3. Upon irradiation with 313 nm light, the colorless crystals 1 and 3 changed to violet and yellow, respectively.

Phase Transition of a Liquid Crystal Induced by Chiral Photochromic Dopants

Abstract A chiral cyclohexane having two photochromic diarylethene unit was synthesized in an attempt to use it as a dopant for a photoresponsive liquid crystal. A stable photoswitching between nematic and cholesteric phases could be induced by the addition of a small amount of the chiral cyclohexane to a nematic liquid crystal 4-cyano-4′-penthylbiphenyl (K-15).

Photoswitching of Helical Twisting Power by Chiral Diarylethene Dopants

Abstract Photochromic chiral compounds having two diarylethene units were synthesized in an attempt to use them as dopants for photoresponsive liquid crystals. Stable photoswitching of the photochromic dopants induced large pitch changes of chiral nematic liquid crystals composed of K-15 and a small amount of the chiral dopants.

Photochromism of 1,2-Bis(3-n-alkyl-1-benzothiophen-2-yl)perfluorocyclopentene Derivatives

Diarylethene derivatives having 1,2-bis(3-n-alkyl-1-benzothiophen-2-yl)perfluorocyclopentene have been synthesized to examine their photochromic properties in solution. All the derivatives underwent photochromism in hexane. The introduction of long-chain substituents to the 3-positions of a 1-benzothiophene unit leads to longer wavelengths of the absorption band of the closed-ring isomer. However, the cyclization quantum yields of these compounds showed no increase with alkyl chain length.

Photochromism of a Chiral Cyclohexane Having Two Diarylethene Chromophores.A Large Optical Rotation Change

A chiral cyclohexane having two diarylethene chromophores was synthesized in an attempt to construct a molecule which shows a large optical rotation change by photoirradiation. Circular dichroism (CD) and optical rotation were found to change dramatically upon photoirradiation.

Photoswitching of helical twisting power by chiral photochromic diarylethene dopants

Two kinds of chiral diarylethene derivatives were synthesized and used as dopants for photoresponsive liquid crystals. Both derivatives underwent thermally irreversible and fatigue resistant photochromic reactions and exhibited reversible circular diochroism (CD) spectral changes. Large photostimulated pitch chances of chiral nematic K-15 liquid crystals were observed by the addition of the derivatives as dopants. The relation between the optical rotation and the twisting power force was discussed.