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Abstract: Three regioisomeric bisbenzothienylethenes equipped with two (R)-pentafluoropropanoyloxyethyl groups on both ends of the hexatriene moiety displayed high diastereoselectivity towards light-induced 6π-electrocyclization reactions, particularly in polar solvents. In non-polar solvents such as hexane and octafluorotoluene, however, diastereoselectivity was not very high owing to the fluorophobic or less fluorophilic interactions, respectively, between the fluoroalkanoyl side chains and the solvent molecules. [ABSTRACT FROM AUTHOR]

Cycloreversion processes of three photochromic fulgide derivatives in toluene solution were investigated by means of picosecond and femtosecond laser photolysis methods. Femtosecond laser irradiation revealed that the cycloreversion processes upon visible one-photon excitation took place within a few ps in these three derivatives. On the other hand, drastic enhancements of the reaction yield were observed under picosecond laser exposure. Excitation intensity effect of the reaction yield and dynamic behaviors revealed that the successive two-photon absorption process leading to higher excited states opened the efficient cycloreversion channel in the three derivatives. The reaction yields in higher excited states were found to be quite large in these three systems, 0.35–0.55, while those in the S1state were 0.048–0.21. The correlation of the reaction yield in the S1state with that in Snstates suggest the character of the electronic states connected by the optical absorption plays an important role in the control of the cycloreversion reaction. [ABSTRACT FROM AUTHOR]

Novel thermally reversible photochromic dihydrobenzothiophenes 1 and 2 , and dihydronaphthalenes 3–6 were synthesized. The colored form 1Q returned to the colorless 1R within 150 min, while the decoloration of 2Q was much slower. On the other hand, dihydronaphthalenes returned very quickly. The decoloration rate was controlled by introducing a methoxy group on the phenyl ring. [ABSTRACT FROM AUTHOR]

Presents information on the experiment on the synthesis of two photochromic (R)-binaphthol-condensed indolylfulgides. Reactions of the photochromic; Results and discussion of the photochromic molecules; Mutual conversion by photoirradiation; Thermal stability and fatigue resistivity toward the iterative photochromic interconversion; Description of the binaphthol-condensed indolylfulgides; Introduction to photochromic materials.

Reports on a diastereoselective photochromic bisbenzothienylene (1O) possessing one stereogenic center in the molecule. Use of allylic strain and electronic repulsion between the substituents in stereoregulation; Design and synthesis of 1O; Observation of four sets of doublets of the secondary methyl group of the conformational isomers; Formation of two diastereomeric 1C from irradiation of racemic 1O.

The introduction of electron-donating groups on the skeleton of a naphthopyran, 3,3-diphenyspiro[benzofluorenopyran-cyclopentaphenanthrene], has led to the development of a photochromic dye applicable to photochromic lenses. Introducing a methoxy group to C6 moved the absorption band of the MC form towards the longer wavelength. Further introduction of methoxy groups to the para-position of the phenyl groups on C3 induced faster decoloration of the MC form. Additional introduction of a methoxy group to C13 led to the enhancement of the absorption intensity as well as the facile, economic synthesis of the dye caused by the symmetrical property of the starting material. [ABSTRACT FROM AUTHOR]

Two new bithiazole-containing diarylethenes, 1-[5-methyl-2-(5-methyl-2-thiazolyl)-4-thiazolyl]-2,5-dimethyl-3-thienyl-3,3,4,4,5,5-hexafluorocyclopentene and 1-[5-methyl-2-(5-methyl-2-thiazolyl)-4-thiazolyl]-2-methyl-3-benzothienyl-3,3,4,4,5,5-hexafluorocyclopentene were synthesized and their photochromic and fluorescent properties have been investigated. They exhibited thermally irreversible photochromism and fluorescent switching in toluene. The effects of complexation of these two compounds with various metal cations such as Na + , Ag + , Hg + , Co 2+ , Ni 2+ , Cu 2+ , Ba 2+ , Zn 2+ , Cr 3+ , Pb 2+ , Cd 2+ , Sn 2+ , Al 3+ , Fe 3+ on photochromic and fluorescent properties were also studied. Metal cations caused small effects on the absorption bands of their ring closed forms. However, fluorescence intensities of both compounds were strongly suppressed by Ni 2+ , Cu 2+ and Fe 3+ . [ABSTRACT FROM AUTHOR]

Six novel photochromic bisarylpyridazinones containing 2,5-dimethylthiophene or 5-methyl-2-phenylthiazole unit were synthesized, and their photochromic and fluorescence properties were investigated. The bisarylpyridazinones underwent reversible color change upon irradiation with UV or visible light. The effect of solvents on the absorption spectra of the bisarylpyridazinones was investigated. The closed-ring forms of bisarylpyridazinones displayed negative solvatochromism which was attributed to the high dipolar characters of the molecule. The open-ring forms of bisarylpyridazinones showed fluorescence at 400–480 nm upon excitation at 302 nm, and the intensities of emission bands gradually decreased during the ring-closing photoreactions. Among the synthesized bisarylpyridazinones, 4,5-bis(5-methyl-2-phenylthiazol-4-yl)-2-methyl(or 2-phenyl) pyridazin-3(2H)-ones ( 5O and 6O ) displayed rather large absorption and emission spectral change, higher quantum efficiency during the photoreaction compared to others. A high conversion ratio (94%) to the closed form was observed for 5O . [ABSTRACT FROM AUTHOR]

Abstract: From 2,3-dibromobenz[f]indenone, four compound: 2,3-bis(5-methyl-2-phenyl-4-thiazolyl)benz[f]indenone 1O, 2,3-bis(3,5-dimethyl-4-isoxazolyl)benz[f]indenone 2O, 3-(3,5-dimethyl-4-isoxazolyl)-2-(5-methyl-2-phenyl-4-thiazolyl)benz[f]indenone 3O and 2,3-bis(5-methyl-2-phenyl-4-thiazolyl)benz[f]indenol 4O were prepared, and their photochromic properties were investigated. Among them, photochrome 1O (weak photochromic) and its bisthiazolylbenz[f]indenol derivative 4O displayed photochromism. During ring closure photoreaction, photochrome 4O showed high conversion ratio (98.4%) with low diastereomeric excess (38%). [Copyright &y& Elsevier]

Abstract: A novel diarylethene having a 1,10-phenanthroline unit at each end of the molecule has been synthesized. Among the metal ions, it formed a stable complex with Cu(I) ions in acetonitrile. Rational structures of the Cu(I) complexes of the colorless and the photo-generated blue form have been given by PM3 semiempirical molecular orbital calculations to be 2:2 cyclic complexes for both isomers, with the complex of the open form belonging to the C2 symmetry group while the complex of the closed form belongs to the D2 symmetry group. Although the ring-closing quantum yield for free diarylethene in acetonitrile was 0.75, that for the complex was 0.026, due to the long distance of the bond-forming carbon atoms in the rigid (open form)2-Cu(I)2 complex. [Copyright &y& Elsevier]

Abstract: 2,3-Bis(5-methyl-2-phenyl-4-thiazolyl)-1,4-naphthoquinone 1- O , its monoethylene acetal 2- O and methylated derivatives 3- O and 4- O were synthesized and their photochromic properties were investigated. While bisarylnaphthoquinone 1- O was nonphotochromic, its monoacetal 2- O and methylated derivatives 3- O and 4- O displayed good photochromism. Among them, the isomer 4- O recorded a remarkable diastereomeric excess (98.40%) with high conversion ratio (96.20%) upon UV irradiation. [Copyright &y& Elsevier]