Porphyrin-containing Catenanes

Porphyrin-containing [2]catenanes have been synthesized by Gunter et al.,1311 following the template-directed synthetic strategy outlined in Figure 15. The bis(hexa-fluorophosphate) salt 15-2PF6 was treated with the dibromide 16 in the presence of the previously formed macrocyclic polyether 22 or 23. After counterion exchange,... 

In other work, the principles discussed above have been applied to the template production of porphyrin-containing [2]-catenanes with, once again, the assembly process being based primarily on n-n interactions but including contributions from both C-H -0 and C-H - Jt hydrogen bonding." " ... 

Figure 5.19 The template-directed, self-assembly of porphyrin-containing [2]-catenanes ...

The target Cu(l)-complexed [2]catenane contains two different macrocycles. Therefore, two routes can be envisaged for its construction by the transition metal templated strategy [64]. They are shown in Fig. 17. Both involve the preparation of an intermediate precatenane species, (C) or (F), in which either Zn or Au porphyrin-containing macrocycle (A) or (E) is threaded onto chelate (B), thanks to copper(I) coordination. Formation of the second, inter-... 

Several examples of photo-active porphyrin-containing catenanes and rotaxanes have been reported recently [84-86], but we will here examine only the few cases based on copper(I) template synthesis of the interlocked structure and as such, strictly related to the structures here discussed [87-90]. These reports, by Schuster and Guldi, present both the synthetic procedure and an account of the photoinduced processes taking place in the array. The latter will be briefly summarized and discussed with reference to the main results on the systems presented in the previous chapters. 

Figure 64. Sequence of reactions leading to [2]-catenane 117, from Zn(ll) porphyrin-containing macrocycle 115 through Cu(l)-complexed precatenate 116.

Figure 16 Protonated ammonium temptation (a) magic ring synthesis of Stoddart s [2]catenane and (b) porphyrin-containing [2]catenane.

For related porphyrin-, azobenzene-, or tetrathiafulvalene-containing catenanes, see (a) Gunter,... 

Other interesting units that have been incorporated in the electron-donor macro-cyclic component of catenanes are porphyrins (Figure 26) [56]. The compounds containing a free-base porphyrins can be protonated in strongly acidic solutions, causing electrostatic repulsions which result in conformational reorientations and changes in rotation rates [57]. 

Several families of porphyrin rotaxanes and catenanes have been synthesized using the classic 3D-template effect of copper(I). The molecules contain up to 5 constitutive organic fragments ([5]rotaxane). By removing the metal template, totally different geometries are obtained. 

A potential for large ring and cavity formation extends to many P-containing organic molecules, in addition to the inorganic phosphates discussed above. These compounds include phosphate derivatives of fashionable structures such as crown ethers, calixarenes, carceplexes, catenanes, rotaxanes, self-assembly molecules and so on, and varieties which are discussed in Chapter 10, such as cyclo-dextrins, phosphosaccharides, phosphoproteins and nucleic acids. Phosphorus analogues of cyclo-polypyridyls and porphyrins are discussed in Chapters 7 and 8. 

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