Photoinduced catalytic system

Vife have extensively studied (10) the photoinduced catalytic system (Figure 2) which is based upon the photochemical generation of cyanide ions from various cyanometa I lates, especially from octa-cyanomolybdate(IV) aod octacyanotungstate(IV) ions. Upon photolysis both compounds form cyanide ions with relatively high quantum yields. Cyanide Sons may act as a catalyst for the dimerizat ion of appropriate heterocyclic carb-2-aldehydes to enediols. Since this photocatalytic system has proved to operate also in solid layers, it may be used for an unconventional photographic process (11,12). 

Figure 2. The photoinduced catalytic system [Mo(CN)g] / heterocyclic carb-2-aldehyde.

We have already seen that photoactive clusters, e.g. CdS, can be introduced into vesicles and BLMs (Sect. 5.2 and 5.3). Similar support interactions are possible with both inorganic and organic polymeric supports. Photoactive colloidal semiconductor clusters can be introduced, for example, into cellulose [164], porous Vycor [165], zeolites [166], or ion exchange resins [167]. The polymer matrix can thus influence the efficiencies of photoinduced electron transfer by controlling access to the included photocatalyst or by limiting the size of the catalytic particle in parallel to the effects observed in polymerized vesicles. As in bilayer systems,... 

The combination of surface-associated reactants with surface-bound H-atoms, occasionally leads to poor photoinduced hydrogenation of the reactant and parallelly to inhibition of H2-evolution. For such systems, tailored bifunctional heterogeneous catalysts have been developed [141], where cooperative catalytic effects are observed in the photohydrogenation reactions. Substitution of ethylene by acetylene, C2H2, in the photosystem composed of Ru(bpy) +/MV2+/Na2EDTA and the Pt colloid results in inefficient hydrogenation of acetylene to ethylene,

[Pg.184]

Since photogenerated MV" " and Ru(bipy) can be used for water reduction and oxidation respectively, it is tempting to examine a system where the two catalytic processes can take place simultaneously following photoinduced electron transfer. As was pointed out above, the RUO2 and Pt cateOysts have to be active enou to intercept the back reaction. Also, their intervention has to be specific in that MV reacts selectively with the Pt particles while RuCbipy) " " interacts with RUD2. Cross reactions have to be avoided since they lead to short-circuitry of the back reaction. 

Photoactivated redox proteins will play important roles in the future development of artificial photosynthetic systems. The unique participation of the protein matrices in photoinduced charge separation and the possibility of implanting catalytic sites in the protein indicate that tailored photoenzymes will be important components for the light-driven synthesis of fuels and valuable chemicals, e.g., CO2 and N2 fixation and amino acid synthesis. The areas of bioelectronics and opto-bioelectronics represent exciting interdisciplinary ventures for chemists, biologists, physicists and materials scientists. The advances in these fields oflFer compelling opportunities for the development of electronic biomaterial-based devices. 

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