Redox photochromism

H. Kamogawa and M. Nanasawa, Redox photochromism involving near-IR, Chem. Lett., 1988, 373-376. 

H. Kamogawa and T. Ono, Redox photochromism in films of viologens, Chem. Mater. 1991, 1020-1023. 

Dinitrogen has been photoreduced to ammonia in aqueous solutions containing colloidal transition metal catalysts (Nahor et al.). Kamogawa and Sato have observed redox photochromism in a crystalline l,r-diaryl-4,4 -bipyridinium salt. 

Heinz Diirr 96.6 Electron Transfer/Redox Photochromism.96-13... 

The photochromic mechanisms of redox-photochromic compounds are usually difficult to determine because they are often multicomponent systems. However, the methylene blue/iron sulfate system is relatively well understood. 

Photochromism Based on Redox Reactions. Although the exact mechanism of the reversible electron transfer is often not defined, several viologen salts (pyridinium ions) exhibit a photochromic response to uv radiation in the crystalline state or in a polar polymeric matrix, for example,... 

The present technique enables light-induced redox reaction UV light-induced oxidative dissolution and visible light-induced reductive deposition of silver nanoparticles. Reversible control of the particle size is therefore possible in principle. The reversible redox process can be applied to surface patterning and a photoelectrochemical actuator, besides the multicolor photochromism. 

The first chapter of the book deals with leuco-spiropyrans and related spiro compounds, which constitute one of the classes of leuco compounds not of the redox type. Such materials are photochromic, and are of major technical importance. The author, Hiroyuki Nakazumi of the Department of Applied Chemistry at the University of Osaka Prefecture, is well known for his researches in functional dye chemistry, particularly photochromic materials, and he provides a very useful update of the field, covering mechanisms, synthesis, spectra and applications, together with a useful section on approaches to near-infrared absorbing photochromic dyes. 

The synthesis of technologically interesting ROMP materials using (233) includes the preparation of molecular wires,701 liquid-crystal polymers,702,703 chiral supports for catalysis,704 redox-active macromolecules,705 photochromic materials706 and embedded clusters of CdSe.707 Polymers... 

To characterize a photochromic redox system the following components of the system should be recognized ... 

When covalently attached to electron transfer active subunits, the DHA-VHF couple can facilitate chemical and physical switching of electronic properties, as a result of photochemically induced rearrangement accompanied by a change in the redox potential. An interesting example of such a switching system is the compound containing a dihydroazulene component and a covalently attached anthraquinone moiety.1311 This system is able to act as a multimode switch, assisted by various processes such as photochromism, reversible electron transfer, and protonation-deprotonation reactions (Scheme 8). 

Scheme9 Photochromic and redox behavior of the DHA/VHF subunit, and the various heteroatomic groups used as substituents at C-2 ofthe five-membered ring.

Polyoxometalates are important catalysts but they are also finding application in optical, electrical, and magnetic devices. Mixed-metal polyoxometalates with vanadium(V) in the polyoxoanion core confers enhanced properties to such structures, principally in their ability to form essentially infinite networks that can be utilized as coatings or as other thin film materials. Additionally, these materials have tunable electromagnetic and photochromic properties. In combination with organic polymers, so-called hybrid polymers, special electrochemical properties are conferred, making possible such electrical storage devices such as capacitors and batteries that utilize the redox properties of the polyoxometalate [7],... 

Fraysse et al. have synthesized a derivative with two ruthenium centers, 29, and have investigated its photochromic and redox properties [27]. The closed form of this complex is obtained with 254-nm light irradiation in 75%... 

Parkhomyuk-Ben Arye, P., Strashnikova, N. V., Iikhtenshtein G. I. (2001) Stilbene photochrome-fluorescence-spin molecules covalent immobilization on silica plate and applications as redox and viscosity probes, J. Biochem. Biophys. Methods (in press)... 

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