Light induced functions

In order to build up dendrimers crqrable of exhibiting redox activity and light-induced functions, appropriate building blocks have to be used. In the last 20 years, extensive investigations carried out on the photochemical and electrochemical properties of transition metal compounds have shown that Ru(II) and Os(ll) complexes of aromatic M-heterocycles (Figure 1), e.g., Ru(bpy)j and Os(bpy)j (bpy = 2,2 -bipyridine), exhibit a unique combination of chemical stability, redox properties, excited state reactivity, luminescence, and excited state lifetime. Furthermore all these properties can be tuned within rather broad ranges by... 

When interaction between the metal-based components is weak, polynuclear transition metal complexes belong to the field of supramolecular chemistry. At the roots of supramolecular chemistry is the concept that supramolecular species have the potential to achieve much more elaborated tasks than simple molecular components while a molecular component can be involved in simple acts, supramolecular species can performIn other words, supramolecular species have the potentiality to behave as molecular devices. Particularly interesting molecular devices are those which use light to achieve their functions. Molecular devices which perform light-induced functions are called photochemical molecular devices (PMD). Luminescent and redox-active polynuclear complexes as those described in this chapter can play a role as PMDs operating by photoinduced energy and electron transfer processes. ... 

Stehlik D. Transient EPR spectroscopy as applied to light-induced functional intermediates along flie electron transfer pathway in photosystem I. In Photosystem I The Light-Driven Plastocyanin Ferredoxin Oxidoreductase. Golbeck J, ed. 2006. Springer, Dordrecht, The Neflierlands. 

In general, molecular-level devices that perform light-induced functions, that is, in which photons act as an energy supply and/or input/output signals, can be termed photochemical molecular devices (PMDs) [2, 4, 9]. The role of light in reference to the relevant features of molecular-level devices will be discussed in more detail in the following section. 

Increasingly systems are investigated in which the photocatalyst, the electron acceptor, and/or the electron donor are linked through molecular bridges. In case of molecular systems, such an appropriate assembly of suitable molecular components capable of performing light-induced functions can be called a photochemical molecular device (Balzani et al., 1987). Such photochemical... 

The aim of this paper is to show that transition metal complexes can be important components to design and build up artificial supramolecular species capable to perform useful light-induced functions. For space reasons, only a few, representative devices will be described, with preference for examples taken from our own laboratories. 

One of the most interesting aspects of supramolecular (multicomponent) systems is their interaction with light. The systems here described show that, in the frame of research on supramolecular photochemistry, the design and construction of nanoscale devices capable of performing useful light-induced functions can indeed be attempted. 

Molecular devices capable of performing light-induced functions (i.e., devices powered by light or capable of elaborating light signals) can be... 

The examples discussed show that coordination compounds, and in particular metal polypyridine complexes, are versatile building blocks for supramolecular systems of photochemical interest. In such supramolecular systems, thermodynamic and kinetic control of intercomponent energy and electron transfer can be achieved by careful choice of molecular components and connectors. By appropriate supramolecular design, simple but interesting light-induced functions can be obtained. 

As already mentioned in the introduction, various fundamental and many empirical results have been published. Although photoelectrochemical cells are easily made, many problems concerning the stability of semiconductors and the function of catalysts still remain to be solved. There are few other approaches such as for instance sensitization (see e.g.) which are not treated here. In addition it should be mentioned that photoelectrochemical systems have been used for light induced synthesis of organic compounds (see e.g.) which could also not be considered in this article. 

This polymer contains carboxylic as well as acrylic functionality. The acrylic part of the polymer undergoes light induced polymerization. Use of this photoreactive polymer eliminated the need for separate acrylic type polymerizable monomer(s). 

Figure 4. Half-life Ti/2of pH gradient decay in the dark as a function of lipid concentration for Mab(Phyt)2 or EPC vesicles after light-induced proton translocation by BR at 2S°C,...

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