Tetraphenyl porphyrin groups

Figure 6. Deviations (AxlO ) from the least squares plane of the macrocycle and in parenthesis, from the plane of the four nitrogens of the cation radical of magnesium tetraphenyl porphyrin (Space group P2][/c, Z 4)...

Unlike the metal atoms in the chalcogenides discussed in the previous section, the iron atoms in iron(II) tetraphenyl porphyrins and the related iron(II) phthalocyanine generally occupy crystallographic sites with symmetry T or 1 only. The exception is the iron site in iron(II) tetraphenyl porphyrin (FeTPP), space group I42d, which has 4 symmetry. 

An example of side-chain fimctionalizahon is the attachment of tetraphenyl-porphyrin carboxylic acid to a fullerene bound steroid (214) via standard EDCl coupling with the hydroxy group of the steroid (Scheme 4.36) [230]. 

Aviv and Gross developed an interesting insertion reaction of diazo compounds into a secondary amine-hydrogen bond in the presence of Fe-corrole complexes (Scheme 7.8) [12], Competition experiments performed in the presence of an amine and an alkene revealed the N—H-insertion reaction to be much faster than the cyclopropanation of the C=C bond. Apart from this chemoselectivity issue, the reactions are characterized by their very short reaction times most insertion reactions were completed within 1 min at room temperature. Most recently, Woo s group reported on a similar process using commercially available iron tetraphenyl-porphyrin [Fe(TPP)] dichloride [13]. 

The porphyrin isomers 3.160 and 3.161 were isolated as by-products in the course of carrying out what were ostensibly normal Rothemund-type tetraphenyl porphyrin syntheses.For instance, the Japanese group isolated 3.160 as a byproduct of the HBr-catalyzed reaction between pyrrole and benzaldehyde. The Polish group, on the other hand, used BF3-(OEt)2 as the catalyst and p-tolylaldehyde... 

Recently, several laboratories have reported stereochemical analysis using NMR spectroscopy of series of MMA oligomers (from unimer to pentamer) prepared by radical polymerization with tetraphenylethane initiators,266 by radical telomerization with thiophenol,267 and by group transfer polymerization.268 These polymerization systems are not stereospecific (rather syndio-tactic) and thus the resultant MMA oligomers consist of comparable amounts of some stereoisomers. Cacioli and co-workers267 prepared MMA oligomers by radical telomerization with cobalt (II) tetraphenyl porphyrin, and studied them using two-dimensional NMR. They isolated three of four possible stereoisomers of the pentamer ( = 3) ... 

Figure 6.2.14 (a) Crystal structure of me o-tetraphenyl porphyrin. The para- hydrogen atom of the phenyl group on the right of the left porphyrin is in van der Waals distance to the perpendicular phenyl ring at the top of the right porphyrin. The perspective does not suggest this, (b) Co-crystal with 1,3-xylene. 

The enzymatic activity of AChE from electric eel is inhibited by monosulfonate tetraphenyl porphyrin (TPPSi) the structure of which can be seen in Figure 12.1 with Rj = SO3, R2 = no substituent group, and no metal incorporated [36]. A Lineweaver-Burk plot of enzymatic rates in the absence/presence of TPPSj determines the type of inhibition resulting from the presence of the porphyrin. The Lineweaver-Burk plot is the plot of the double-reciprocal form of the initial enzymatic rate versus the substrate concentration. Intersection of the lines generated in the absence and presence of inhibitor at the y-axis shows no change in maximal velocity but a change in the Michaelis constant K j, an indication of the substrate binding affinity, and indicates competitive inhibition by the porphyrin. Competitive inhibition involves competition of the inhibitor for occupation of the active site of the enzyme. 

The most famous monopyrrole polymerization route to obtain p>orphyrins involves the synthesis of tetraphenyl porphyrins, from reaction between pyrrole and benzaldehyde (Atwood et al., 1996). This procedure was first developed by Rothemund (Rothemund, 1935) and, after modification by Adler, Longo and colleagues (Adler et al., 1967), was finally optimized by Lindsey s group (Lindsey et aL,1987). In the Rothemund and Adler/Longo methodology the crude product contains between 5 and 10% of a byproduct, discovered later to be the meso-tetraphenylchlorin which is converted in the product under oxidative conditions (Fig. 2). 

Ruthenium phthalocyanine 49 (R = -H, M = Ru(II)) monolayers were obtained by self-assembly on pyridyl-functionalized SiOa or AI2O3 substrates by coordination between Ru and the pyridino group to obtain 63 [155]. The pyridino-functionalized metal oxides were dipped into a solution containing the more soluble benzonitrile derivative of the phthalocyanine RuPc(NC-C6H5)2, and ligand exchange reactions led to 63. Strategies have been described to immobilize a second layer of a Ru-phthalocyanine or a Co tetraphenyl-porphyrin. 

SWCNTs-porphyrin nanosensors have been fabricated for monitoring toxic substances in the enviromnent [215], Free-base, Ru and Fe octaethyl-and tetraphenyl-substituted porphyrins provided good selectivity and sensitivity to various VOCs tested (acetone, butanone, methanol, ethanol). Nonco-valently functionalized SWCNTs with iron tetraphenylporphyrin were used for benzene detection [216], SWCNTs noncovalently functionalized with copper phthalocyanine and free-base porphyrins were used as sensing layers for the detection of toluene [217]. Also, MWCNTs were used as sensors for benzene, toluene, and xylene, when fnnctionalized with metal tetraphenyl porphyrins [218], SWCNTs-poly(tetraphenylporphyrin) hybrid was prepared and tested as a low-power chemiresistor sensor for acetone vapor [219]. A chemiresistive sensor array was fabricated from SWCNTs noncovalently functionalized with metallo mcxo-tetraphenylporphyrins (Cr(III), Mn(III), Fe(III), Co(III), Co(n), Ni(n), Cu(II), and Zn(II)) [220]. Its responses were treated by statistical analyses and allowed to classify VOCs into five classes alkanes, aromatics, ketones, alcohols, amines. Amines detection as an indicator of meat spoilage was achieved by the same group with the same sensor array [221]. 

A [5]rotaxane 10, based on a meso-tetraphenyl porphyrin and synthesized in 85% yield, showed similar pH-driven switching properties, depicted in Scheme 14.5. When all the nitrogen atoms of the amino groups are protonated, CB[6] prefers to encapsulate the protonated diaminotriazole site (state I) because of the strong ion-dipole interactions between ammonium ions and carbonyl functions at the portal of CB[6]. On the other hand, after complete deprotonation of the molecule, CB[6] resides mostly on the relatively more hydrophobic benzyl part, thanks to hydrophobic effect (state II). 

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