Photosynthetic antenna system components

A particularly intriguing kind of supramolecular self-assembly by axial coordination to metaUoporphyrins, namely self-complementary coordination, is reviewed in the second chapter by Yoshiaki Kobuke. Self-complementarity affords large stability constants. The fascinating systems described in Kobuke s contribution were prepared and investigated as models for components of photosynthetic natural systems self-complementary dimers of porphyrins mimic the special pair of the photosynthetic reaction centers, while macrocychc and three-dimensional porphyrin supramolecules were prepared as photosynthetic antenna models. 

The assembly of molecular components for light harvesting and charge separation in artificial photosynthetic systems is of current interest. To mimic the multistep electron transfer in natural systems, Imahori et al. prepared a mixed SAM that combines an artificial antenna system (pyrene) with an artificial reaction centre (porphyrin), to examine the possibihty of photoin-duced energy transfer in two-dimensional assemblies (Fig. 29, 20) [27,147]. The ratio of porphyrin pyrene in the mixed SAM estimated from the absorption spectra on the gold surface is significantly lower than that of the solution from which the SAM was prepared. The strong tz-tz interaction of... 

Even a relatively simple bacterial photosynthetic system is very complex and its synthetic imitation is a challenging task. Mimicking of the natural photosynthetic process requires synthetic models of all the crucial components and linking them together into a working molecular assembly. All the elements (antenna, charge separation, and reaction centres) may involve transition metals. Application of metal complexes facilitates mimicking of this complex chemical system due to rich and versatile photochemical processes typical for transition metal complexes (see section 6.4 in Chapter 6) [48]. 

Loiseau F, Marzanni G, Quiei S, Indelli MT, Campagna S (2003) An artificial antenna complex containing four [Ru(bpy) ]2+-type chromophores as light-harvesting component sand a [Ru (bpy)(CN)" ]2- subunit as the energy trap. A structural motif which resembles the natural photosynthetic systems. Chem Commun 286-287... 

---