Self-Assembling Multiporphyrin System

Although there have been several approaches to porphyrinic catenanes and rotaxanes [46-48], these have been based on assembly through charged [49] or neutral [50,51] 7r-donor/acceptor concepts, or by using coordination chemistry [47]. Nevertheless, there is a series of non-porphyrinic amide-based catenanes and rotaxanes that have received considerable attention [52,53]. The primary recognition factor in these systems is H-bonding. Gunter [54] has extended these systems to include porphyrinic supramolecu-les that use similar H-bonded amide-based motifs for the self-assembly of multiporphyrin catenanes and rotaxanes. 

Before discussing self-assembling systems, it is necessary to roughly survey some typical examples of covalently linked multiporphyrin systems because they provide prototypes of artificial multiporphyrin systems and some of them may be useful as components for further large-scale assemblies. 

Figure 17. Various types of self-assembling processes of multiporphyrin systems.

The most used approaches for the construction of multiporphyrin systems are the self-assembly methods. For example, electrostatic assembly is an easy and widely used method based on the interaction of oppositely charged porphyrins for preparation of more complex systems [1-12]. Self-assembly of porphyrins are also possible by coordination of nucleophihc groups to the central metal ion or using compounds having two nucleophihc sites to coordinate two metalloporphyrins [13-22]. These methods have been used not only for the preparation of porphyrin dimers and trimers, but also for the formation of larger supramolecular networks. Despite the apparent simphcity of the preparation methods of multiporphyrin materials by self-assembly, they generally are less stable as compared to covalently bond... 

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