Porphyrin-based dendrimer

Porphyrin-based self-assembled molecular squares 389 can form mesoporous thin films in which the edge of a square, thus the size of the cavity, can be adjusted by appropriate choice of substituents [8]. Fibers that form coil-coiled aggregates with distinct, tunable helicity are built from crown ethers bearing porphyrins 390 [9]. In addition to the porphyrin applications discussed in Sections 6.3.2.2 and 6.4, dendrimer metalloporphyrins 391 to be applied in catalysis [10] and the water-soluble dendritic iron porphyrin 319 modelling globular heme proteins [11] can be mentioned. 

Other porphyrin-based dendrimers will be found in Section 5.2. 

Other groups have also studied such macrocycles. For example, extending the molecular chain with a single carbon that connects the dendrimers with the porphyrins on the outer shell (Fig. 5.13) resulted in a significant improvement in the electron transfer process [67]. The authors reported that only 10% of the excitation intensity was needed for 64 Zn(II) porphyrin-based structure with a longer connecting chain to... 

Figure 47. Porphyrin-containing dendrimer (87) based on core 85 and porphyrin 45 as peripheral unit.

Figure 142. Binding of axial ligands to dendrimer porphyrins log(fCq) values for a series of nitrogenous bases with various sha ses.

Figure 4 (a) Organic dendrimers Fullerene-based dendrimer. (Reproduced -with permission from Ref. 44. Royal Society of Chemistry, 2009.) (b) Zn Porphyrin-based... 

Figure 14 Examples of protein surface mimics. A caiix[4]aiene (9) developed by Hamiiton et al a porphyrin-based proteodendrimer (10) prepared by the Tsukube group, showing both the first geuCTation (biue) and second generation (red) of the dendruner, R = second generation dendrimer and a tetrasubstituted porphyrin scaffold (11) used by the Hamilton group.

Figure 8.10 The porphyrin-based dendrimer described [56] by Frechet and co-workers that has potential applications as a photodynamic therapy agent.

Sugiura K (2003) An Adventure in Macromolecular Chemistry Based on the Achievements of Dendrimer Science Molecular Design, Synthesis, and Some Basic Properties of Cyclic Porphyrin Oligomers to Create a Functional Nano-Sized Space. 228 65-85 Sun J-Q, Bartlett RJ (1999) Modern Correlation Theories for Extended, Periodic Systems. 203 121-145... 

A poly(L-lysine) dendrimer 23 which carries 16 free-base porphyrins in one hemisphere and 16 Zn porphyrins in the other has been synthesized and studied in dimethylformamide solution [54]. In such a dendrimer, energy transfer from the Zn porphyrins to the free-base units can occur with 43% efficiency. When the 32 free base and zinc porphyrins were placed in a scrambled fashion, the efficiency of energy transfer was estimated to be 83% [55]. Very efficient (98%) energy transfer from Zn to free-base porphyrins was also observed in a rigid, snowflake-shaped structure in which three Zn porphyrin units alternate with three free-base porphyrin units [56]. 

Alternatively, the quencher can be directly connected to the dendrimer structure. The photophysical behavior of generation 1,2 (compound 29), and 3 dendrimers containing a free-base porphyrin core and 12, 36, and 108 peripheral anthraquinone units, respectively, was studied in chloroform and dimethylac-... 

Other supramolecular structures such as dendrimers have also been synthesized with zinc-containing porphyrins. Sixteen free base and sixteen zinc porphyrin units were added at the fifth generation of dendritic poly(L-lysine) and intramolecular fluorescence energy transfer was observed.823 Assembly of supramolecular arrays in the solid state has been achieved with the incorporation of an amide group for hydrogen bonding. Zinc meso-tetra(4-amidophenyl)porphyrin... 

Two dendrimers based on Fe-porphyrin core carrying peptide-like branches of different sizes have been synthesized in order to have more open and a more densely packed (23) structures [43]. The electrochemical behavior has been examined in CH2C12 and in aqueous solution. In the less polar solvent, the two dendrimers show similar potentials for the Fem/Fen couple, suggesting that the iron porphyrins in both the more open and the more densely packed dendrimers experience similar microenvironments. On the contrary, in water the behavior of the two dendrimers is very different since the reduction from Fem to Fe11 is much easier for the densely packed dendrimer. This result can be explained considering that in the dendrimer with the relatively open structure the aqueous solvation of the iron porphyrin is still possible, whereas in the densely packed one the contact between the heme and the external solvent is signifi-... 

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