Photofunctional molecules

The photophysics and photochemistry of d transition metal complexes, such as Re(I), Ru(II), Os(II), and Ir(III), with a-diimines as electron acceptor ligands have been widely investigated during past four decades. These complexes have been frequently used as photofunctional molecules because of the following common properties (1-16) ... 

Photochemical reactions proceed in the gas phase, in solution, and even in the solid state. Photochemical reactions in the solid state are especially important when considering the applications of photofunctional molecules in materials, where photophysical processes and photochemical reactions are used to trigger some change in a given physical property of a system, such as its color, solubility, or electroconductivity. 

Poly(benzyl ether) dendrimers have several unique optical and photochemical properties. In particular, it is quite interesting that some photochemical events are considerably affected by the molecular size and morphology of the dendrimer molecules. These examples, together with those by other researchers [2], will provide a new strategy toward next-generation, nanoscopic photofunctional materials. 

G. Calzaferri, Dye Molecules in Zeolite L Nano Crystals for Efficient Light Harvesting. In Photofunctional Zeolites, et. M. Anpo, NOVA Science Publishers, New York, 2000, 205-218. 

Azobenzenes have simple chemical structures and exhibit simple photoisomerization between the trans- and cis form. However, they can really provide various photofunctions by their combination with sophisticated systems such as Ch LCs. The Ch LCs have a good potential for display applications, because they show interesting optical properties depending on the helical structures and the textures. Many types of optical materials can be created by the use of the photoisomerization of chiral azobenzenes in the Ch LCs. New ideas, including design of molecules and systems, may allow us for future materials not only in the field of optics but also in other fields. 

The change in the absorption spectrum and the molecular structure on photoisomerization of azobenzenes can be used for practical applications. The literature on possible applications in photoresponsive materials was reviewed up to 1988 by Rau. Important contributions by Japanese workers, for example, on light-driven potassium ion transport through membranes by means of crown ethers with a photofunctional azobenzene cap, were recently summarized by Shinkai. Moreover, light-manipulation of other super molecules based on azobenzene photoisomerization is described in the book by Feringa. " The E— Z photoisomerization for the preparation of thermally unstable Z-isomers for use as kinetic probes in microheterogeneous media was described in Section 89.5. 

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