Electro photochromism

Electro-photoswitching devices possess a dual mode operation resulting from different electrochemical properties in the two photo-interconvertible states. They may display both photochromism and electrochromism. They allow the photomodulation of electrochemical properties as was shown to occur in photochromic dihydroazulene derivatives [8.247]. Separate photochemical and electrochemical interconversion has been realized in systems containing a photoactive azo [8.248, 8.249] or dihydroazulene [8.250] unit appended with an anthraquinone moiety. 

Switching systems based on photochromic behavior,I29 43,45 77-100 optical control of chirality,175 76 1011 fluorescence,[102-108] intersystem crossing,[109-113] electro-chemically and photochemical induced changes in liquid crystals,l114-119 thin films,170,120-1291 and membranes,[130,131] and photoinduced electron and energy transfer1132-1501 have been synthesized and studied. The fastest of these processes are intramolecular and intermolecular electron and energy transfer. This chapter details research in the development and applications of molecular switches based on these processes. 

There are many functional molecules, and their functions, such as electro-chromism, photochromism, photoelectric conversion, chemiluminescence, catalyst, molecular recognition (sensor) etc., are all attributed to a deviation or a change in electronic structure or state of these molecules. For their materializations, conducting polymers are considered to be suitable matrices because their conductive properties and compatibilities to mole-... 

Specific colour change phenomena are named using the suffix chromism and a prefix that describes the stimulus causing the change. Table 1 provides a list of phenomena and the stimulus involved, lonochromism, thermochromism, photochromism, and electro-chromism are the most extensively studied. The others listed are generally less well-established and have either experienced limited commercial exploitation or are essentially academic curiosities. Indeed, the list in the table is probably not exhaustive. 

Darcy, P.J., Heller, H.G., Strydom, P.)., and Whittall, J. (1981) Photochromic heterocyclic fulgides. Part 2. Electro-cyclic reactions of (e)-2, 5-dimethyl-3-furylethylidene(alkyl-substituted methylene)succinic anhydrides. J. 

Attention is focused on carotenoids and polyenes, which are known to be chemically very unstable as isolated entities but to acquire great stability when they are suitably surrounded by a protein cage and become the active elements in the mechanism of vision and photosynthesis. The CL dependence of the in situ Raman spectra of the carotenoids as naturally occurring pigments in bird feathers was studied by Veronelli et al. [65]. Later attention was focused on the bacterial membrane protein bacteriorhodopsin (bR). a small protein (—26,000 daltons) whose potential application in optical and electro-optical devices has been explored by many authors. The justification of such interest lies in the fact that bR contains all-/rfl/ .v retinal, which acts as a lightabsorbing center and makes bR a naturally reversible photochromic system. All-optical switching can be achieved by proper illumination of bR with yellow or blue light. 

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