Multiporphyrin surface assemblies

Self-assembly principles of the formation of multiporphyrin arrays are extended to anchor the porphyrin triads on semiconductor CdSe/ZnS quantum dot (QD) surface. Comparing with individual counterparts (QD, pyridylsubstituted porphyrin H2P(p-Pyr)4, and Zn-octaethylporphyrin chemical dimer (ZnOEP Ph), the formation of heterocomposites QD-porphyrin triad results in the specific quenching of QD photoluminescence, accompanied by the dimer fluorescence strong quenching (Tsd 1-7 ps due to energy and/or electron transfer) and the noticeable decease of the extra-ligand H2P(p-Pyr)4 fluorescence efficiency by 1.5-2 times via hole transfer H2P—>dimer. 

Recently, we have shown that the supramolecular approach (a non-covalent two-fold extra-ligation in conjunction with Zn-porphyrin chemical dimers and trimers) can be successfully employed to create a variety of multiporphyrin structures capable of the fast effective intra-complex energy migration and photoinduced electron transfer [5]. Following this self-assembly principle we have succeeded to anchor in pyridyl substituted porphyrin molecules on CdSe/ZnS QD surfaces. In this case, CdSe/ZnS QDs show luminescence quenching induced by dynamic and/or static interactions between QD and porphyrins depending critically on sample stability, temperature and solvent polarity [6]. The general focus of this contribution is devoted to demonstrate the... 

While the approaches summarized above limit the number of active chromo-phores in the vicinity of the surface, the attachment of multiporphyrins more closely resembles the natural process of photon collection. Two recent papers by Kobuke illustrate this approach quite well and take advantage of the axial imidazole binding to zinc porphyrins . The phenomenon is better described by the more recent example in which a heterodimer is formed by self-assembly after the attachment of a zinc porphyrin to a gold surface, as depicted in Figure 13.81 . 

---