Porphyrin dendritic

Porphyrin complexes are particularly suitable cores to construct dendrimers and to investigate how the behavior of an electroactive species is modified when surrounded by dendritic branches. In particular, dendritic porphyrins can be regarded as models for electron-transfer proteins like cytochrome c [42, 43]. Electrochemical investigation on Zn-porphyrins bearing polyether-amide branches has shown that the first reduction and oxidation processes are affected by the electron-rich microenvironment created by the dendritic branches [42]. Furthermore, for the third generation compound all the observed processes become irreversible. 

Recently, Kimura et al. have reported the encapsulation of electro chemically and photo chemically active groups such as a porphyrin unit (51) or a ruthe-nium(II) bis(terpyridyl) (52) unit in the interior of a 1,3,5-polyphenylene-based dendritic structure (Scheme 21). The dendritic porphyrins have been synthesiz-... 

Ru(CO)(den-por) (den-por=dendritic porphyrins). These are made by condensation of Ru(CO)L (L=5,10,15,20-tetrato(4 -hydroxyphenyl)porphyrin or 5,10,15,20-tetrakis(3, 5 -dihydroxy-phenyl)porphyrin), themselves made from RUjlCO) and (L), with poly-(benzylether) dendrons H, C NMR, electronic and IR spectra of the products were measured. Epoxidation of cyclic alkenes, cis- and tranx-sfilbene, styrene and its 3-methyl, methoxy, chloro and bromo derivatives, dimethylchromene and of cholesteryl esters in high yields and turnovers was effected by RulCOKden-porl/lCl pyNOl/CHjClj [871]. 

Dendritic derivatives of these macrocycles can be placed in the wider context of studies on metalloporphyrins with sterically hindered faces which have been designed in attempts to mimic the properties of heme proteins and chlorophylls, and there are suggestions that steric isolation of the metalloporphyrin nucleus is important in certain biological functions, The redox properties of metalloporphyrins are well-documented they are dominated by two, reversible one-electron transfers involving both the metal and the ligand. The first dendritic porphyrins of general structure 47 and their Zn complexes were reported by Inoue et al. who... 

Covalent coupling A pre-existing metal complex is coupled covalently with den-drons and is thus surrounded by a dendritic shell. Appropriate examples are the redox-active metallodendrimers of Kaifer et al. [117] or the dendritic porphyrin/ metal complexes prepared and characterised by Diederich et al. [118] and Aida et al. [119]. 

Fig. 8.7 Dendritic porphyrin-metal complex (according to Diederich et al.)...

Dandliker, P. J. Diederich, F. Gross, M. Knobler, C. B. Louati, A., Sanford, E., (1994) Dendritic porphyrins Modulating redox potentials of electroactive chromophores with pendant multifunctionality ... 

Another example of a rigid macrocycle used as the central core of a den-drimer is the porphyrin. First and second generation phenylene-based dendritic porphyrins with 8 and 16 long alkyl chains on their periphery have been studied (Fig. 80). Only the second generation exhibits mesomorphic behavior with the formation of a rectangular columnar mesophase upon heating (Cr 39 Coir 110 I) [334]. A stable supramolecular 1 1 complex was formed between the second generation and Ceo, which led to the enhancement of the mesophase stabiUty of the formed (imidentified) columnar phase (Cr 99 Col 250 I). 

The dendritic molecule 12 with an integrated porphyrin core and a catechol surface could be dissolved in acetonitrile. Its fluorescence was easily quenched by vitamin K3, which presumably finds accommodation within the micellar core. Attempts to dissolve a porphyrin within the porphyrin micelle failed. They are too large and cannot interact with the dendritic porphyrin . 

A dendritic porphyrin receptor for C60 which features a profound positive allosteric effect. Angew. Chem.. Int. Ed. 31. Engl. 2002. 41, 2790-2792. 

Fig. 3 Example of dendritic porphyrin complexes mimicking hemoglobin as proposed by Diederich and coworkersd (a) amide dendrons (b) ester dendrons.

Cytochrome P450 is one of nature s oxidative workhorses, and it is involved in a wide variety of biological reactions, one of the most important being the detoxification of foreign bodies within the liver. A wide variety of approaches was developed to design and construct synthetic model systems of the cytochrome P450 family.They vary from the earlier mentioned "capped" and "picnic basket" porphyrins, over supramolecular cytochrome P450 models, to dendritic porphyrins. ... 

Christie and Kompella 2008). PDT encompasses the systemic administration of photosensitizers with the local use of light to target specific diseased sites (Nishiyama et al. 2003). Ionic dendritic porphyrins mixed with PEG-i/ocA -poly(L-lysine) have thus been investigated for their potential application in PDT. Porphyrins are chromophores which can fluoresce and signal reaction occurrence (Pasternack et al. 1993). Upon photoirradiation, the dendritic porphyrin-loaded micelles showed similar oxygen consumption results as free dendritic porphyrin in phosphate buffered saline and BSA (Nishiyama et al. 2003). However, the micelles containing the porphyrin molecules underwent a drastic increase in photocytotoxicity when exposed to cells compared to the free porphyrin molecules. 

Figure 13.42. Weakly coupled large dendritic porphyrin arrays.

Dandliker PJ, Diederich F, Gross M, Knobler CB, Louati A, Sanford EM (1994) Dendritic porphyrins modulating redox potentials of electroactive chromophores with pendant multifunctionality. Angew Chem Int Ed 33(17) 1739-1742... 

Mongin, 0. Papamicael, C. Hoyler, H., and Gossauer, A. (1998). Modular Synthesis of Benzene-Centered Porphyrin Trimers and a Dendritic Porphyrin Hexamer. J. Org. Chem., 63, 5568-5580. 

Schlundt S, Kuzmanich G, Spanig F, et al Dendritic porphyrin-fifllerene conjugates efficient light-harvesting and charge-transfer events, Chem EurJ 15 12223—12233, 2009. 

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