摘要:

This work is devoted to photoresponsive hybrid organic-inorganic materials prepared by the sol-gel method, using dithienylethene or azobenzene as photosensitive chromophores. These photochromic units were covalently attached to the silica backbone as part of the main-chain and as a side group respectively. The electrocyclization of dithienylethene or the isomerization of azobenzene under irradiation cause local modifications of the optical properties of the host sol-gel polymers We took advantage of either high refractive index changes (>10−2) or material deformation of the sol-gel films to design optical components and to store information.

ISSN:1058-725X    

DOI:10.1080/10587250008023817

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Photochromic ring-closure reactions of diarylethene derivatives with terthiophene (T3H, T3Me) have been examined by femtosecond transient absorption spectroscopy. The rate of the ring-closure reaction of T3H in n-hexane was estimated to be ∼ 2.5 ps, which is very similar to that of T3Me in the same solvent. It was suggested that the ring-closure reaction proceeds through a concerted mechanism without any intermediates but not a two-step mechanism. The rate of ring-closure reaction was also dependent on the solvent polarity, suggesting that the charge transfer state in the excited singlet state plays an important role in the photochromic reaction.

ISSN:1058-725X    

DOI:10.1080/10587250008023818

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

This paper reports on materials whose second order nonlinear optical (NLO) properties can be switched by light. We synthesized and studied the properties of a series of substituted N-salicylidene anilines which are noncentrosymmetric and photochromic crystals. All compounds exhibit second harmonic generation (SHG). One of the compounds exists in two different cristalline forms, one being photochromic and the other thermochromic. Photoswitching of SHG was performed : irradiation by UV light lead to a decrease of SHG up to 60% of the SHG signal at 1064 nm and 10% at 1907 nm.

ISSN:1058-725X    

DOI:10.1080/10587250008023819

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Magnetic and photochromic behaviors of cobalt-iron polycyanide (Na0.34Co1.33Fe(CN)6·4.5H2O) were investigated. This compound changes its spin state via photo-induced charge transfer between a low spin state of FeII(S= 0)-CN-CoIII(S= 0) and a high spin state of FeIII(S= 1/2)-CN-CoII(S= 3/2). The spin transition is accompanied by a color change, indicating a potential application for novel photochromic material.

ISSN:1058-725X    

DOI:10.1080/10587250008023820

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

3,3-Diphenyl-9,10-di-n-undecyloxypyrano[3,2-a]phenazine3was designed to be incorporated into fibres of 2,3-di-n-undecyloxyphenazine which display gel-forming ability in various fluids. A spectrokinetic study and the determination of the temperatures of gel-to-sol phase transition, give evidence of the insertion of the photochromic chromene into the organogelator network. Under continuous irradiation, the photochromic reaction induces a decrease of the gel strength which can be used to trigger the gel-to-sol phase transition.

ISSN:1058-725X    

DOI:10.1080/10587250008023821

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Photo-orientation by photoisomerization is quantified for individualizable photoisomers of diarylethene and spiropyran-type chromophores introduced into poly-methyl-methacrylate films. We have measured isomers optical transitions relative orientations, and photochemical quantum yields in these photo-anisotropic films.

ISSN:1058-725X    

DOI:10.1080/10587250008023822

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Monolayers of ternary ion-paired macrocyclic amphiphiles consisting of a tetracationic cyclophane and two kinds of sulfonate surfactants with an azobenzene unit and either a single or double long chain alkyl unit were prepared by a Langmuir-Blodgett technique to elucidate the structure/property relation between a free space surrounding an azobenzene moiety and photoisomerizability in monolayers. It was found that an azobenzene unit with a hexyl group needs a minimum occupied area of about 0.5 nm2for sufficientE/Zphotoisomerization.

ISSN:1058-725X    

DOI:10.1080/10587250008023823

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The spectral and kinetic characteristics for a number of ferrocenyl substituted naphthopyrans as compared with diphenyl substituted analogs are presented. The effect of the ferrocenyl substituent on photoinduced absorption and luminescent properties as well as the kinetic characteristics of photochromic transformations and photodegradation was studied.

ISSN:1058-725X    

DOI:10.1080/10587250008023824

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A dinuclear ruthenium photochromic complex, based on the dithienylperfluorocyclopentene unit, has been prepared following a building block approach, by palladium-catalyzed Sonogashira-Hagihara cross-couplings. At 254 nm, a photostationary state occurs, characterized by 75% of ring closure. Upon oxidation to mixed-valence species, theopenisomer displays no intervalence (IV) band, while for theclosedone, an IV band corresponding to a 0.025 eV electronic coupling parameter is observed, as well as a thermal reopening of the cyclohexadiene moiety. Extended Hückel calculations have been performed on model complexes in order to rationalize this efficient switching effect, and also the unexpected unstability of the oxidizedclosedisomer.

ISSN:1058-725X    

DOI:10.1080/10587250008023825

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A Malachite Green derivative incorporating a bis(monoazacrown ether) structure enables efficient photocontrol of metal ion complexation. Its photochromism in the presence of alkali metal ions is examined by kinetics measurements and molecular-orbital (MO) calculation.

ISSN:1058-725X    

DOI:10.1080/10587250008023826

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor