Porphyrins amino functionalized

Compound 2 was furthermore employed in the preparation of NH-linked Pc-porphyrin arrays [60]. The reaction between the amino-functionalized porphyrin 8 and 4-iodophthalonitrile using Buchwald-Hartwig amination conditions (Pd(OAc)2/ rac-BINAP (BINAP = 2,2/-bis(diphenylphosphino)-l,l/-binaphthyl) as the catalytic system) in the presence of potassium fe/7-butoxide, delivered the entities connected either at the meso-phenyl group (9 in Fig. 7) or at the /1-pyrrolic position [61]. 

Figure 3.24 Schematic diagram describing the covalent attachment of an amino functionalized porphyrin to acyl chloride derivatized carbon (top) and Pt surfaces (bottom).

Reaction of 217 with Cjq leads to the amino-protected porphyrin-fulleropyrroli-dine, which can easily be deprotected to the corresponding amine [229, 277]. By further functionalization via amide coupling an easy access to extended donor-acceptor systems is possible. A carotene-porphyrin-fullerene triad was prepared by reaction of the amine with the appropriate carotene acid chloride. The motivation for the synthesis of all these donor-acceptor systems is the attempt to understand and imitate the photosynthetic process. On that score, a model for an artificial photosynthetic antenna-reaction center complex has been achieved by attaching five porphyrin cores in a dendrimer-like fashion to the fullerene [242]. 

It is shown [100] that polyhalide derivatives of iron and manganese porphyrin catalysts applied on Si02 and polymeric matrices via their amino functional group were successfully synthesized. 

Membrane-s )Anmn have been prepared. Tetraphenylpor-phyrins having jc-carboxy and jc-amino functionalities have been polymerized interfacially to produce chemically asymmetric membrane films.Mercaptoporphyrins have also been polymerized to form ultrathin films of a porphyrin homopolymer based upon 5,10,15,20-tetrakis-(Q -mercapto-j9-tolyl) porphyrin,and thiol-derivatized porphyrins for attachment to electroactive surfaces have been prepared and examined as means of information storage,including those having a ferrocenyl moiety appended in several ways. Various means of linking porphyrins to form arrays have been reviewed. Preparation and investigation of the physical properties of cyclic tetra-, hexa-, hepta-porphyrin and star-shaped multiporphyrin or star-shaped tetra- or octa-porphyrin, or monophthalocyanine arrays have been described and reviewed. As part of this work, methods of forming porphyrins in the presence of acid-labile metalloporphyrins that provide a new route to mixed-metal multiporphyrin arrays have been reported. ... 

Glycine (Gly or G) (aminoacetic acid, aminoethanoic acid) is a nonpolar, neutral, aliphatic amino acid with the formula HOOCCH(NH2)H. Gly is the simplest amino acid and plays important roles in peptide and protein chains. It does not contain a side chain and can thus fit into secondary structures where larger amino acids cannot. Gly acts as a transmitter in the CNS where it accomplishes several functions. Gly is a precursor of porphyrins. Gly, Pro, aspartate, Ser, and Asn enable reverse turns. The acylated amino group of Gly can accept a second acyl group to give rise to a diacylamide. ... 

While these complex model heme proteins have a large potential for functionalization, an interesting approach that is very different has been taken by other workers in that the heme itself functions as the template in the formation of folded peptides. In these models peptide-peptide interactions are minimized and the driving force for folding appears to be the interactions between porphyrin and the hydrophobic faces of the amphiphiUc peptides. The amino acid sequences are too small to permit peptide-peptide contacts as they are separated by the tetrapyrrole residue. These peptide heme conjugates show well-re-solved NMR spectra and thus well-defined folds and the relationship between structure and function can probably be determined in great detail when functions have been demonstrated [22,23,77]. They are therefore important model systems that complement the more complex proteins described above. 

Many important biomolecules are derived from amino acids. Glycine is a precursor of porphyrins. Degradation of iron-porphyrin (heme) generates bilirubin, which is converted to bile pigments, with several physiological functions. 

The search for RNAs with new catalytic functions has been aided by the development of a method that rapidly searches pools of random polymers of RNA and extracts those with particular activities SELEX is nothing less than accelerated evolution in a test tube (Box 26-3). It has been used to generate RNA molecules that bind to amino acids, organic dyes, nucleotides, cyano-cobalamin, and other molecules. Researchers have isolated ribozymes that catalyze ester and amide bond formation, Sn2 reactions, metallation of (addition of metal ions to) porphyrins, and carbon-carbon bond formation. The evolution of enzymatic cofactors with nucleotide handles that facilitate their binding to ribozymes might have further expanded the repertoire of chemical processes available to primitive metabolic systems. 

In addition to serving as building blocks for proteins, amino acids are precursors of many nitrogen-containing compounds that have important physiologic functions (Figure 21.1). These molecules include porphyrins, neurotransmitters, hormones, purines, and pyrimidines. 

The most common functional templates are those of simple amino compounds 4, amino acids 5, and dipeptides 8 (Scheme 3). The simplest amino templates, the tris(ethylene amine) ammonia types 6, 7, and 9 first used in organic dendrimers, have only just begun to be applied in forming peptide dendrimers. Constrained and usual amino acids and heterocyclic compounds such as porphyrin 13, have also been reported.1691... 

All the proteins described in this chapter and that catalyze very different reactions involving 02 exhibit the following common characteristics (1) the presence of an iron porphyrin cofactor, (2) an axial iron ligand coming from the protein that is in most cases a histidine imidazole (except for cytochrome P-450), and (3) the intermediate formation of high-valent iron-oxo species, formally equivalent to Fe(IV)=0 or Fe(V)=0, which are key intermediates in the enzymatic reactions. The different reactions performed by these iron-oxo species and the different uses of 02 by the hemoproteins are due to the very different environments of the heme in these hemoproteins and to a more or less rapid electron transfer. As a function of its environment, the iron-oxo species may either be reduced into H20 if electrons are easily transferred to the heme or oxidize a substrate or a protein amino acid that could be present in close proximity in the active site (Figure 14). 

Another interesting work conducted by Wamser and co-workers in the field of porphyrin monomer sensitizers is the functionalization of tetraphenylporphyrin at the para positions of -phenyl with one amino group and three carboxylic acid groups. The resulted asymmetrical porphyrin (45) can be successfully fabricated into a modified solid Gratzel type cell with polyaniline as the solid electrolyte. The overall energy conversion efficiency of this cell is about 2% with a number of opportunities to optimize the efficiency remaining [81]. 

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