Octakis porphyrin

Ghosh et al. reported that the XPS (X-ray photoelectron spectra) of porphyrins distinguishes the unprotonated (N Is peak at 398.6 eV) from the protonated central nitrogens (N Is at 400.7 eV) in octakis(AUV-diethy lcar-boxamido)porphyrin (93JOC6932). The observation of a pair of MCD (magnetic circular dichroism) bands of opposite sign within the transition of monoacetylporphyrins is probably related to the existence of an equilibrium between tautomers (83TL2433). 

The thermal behavior of an analogous series of octakis(alkoxyethyl)porphyrins was also investigated for comparison ((22) M = 2H, Zn, Cu, Pd, Cd, n = 4, 6, 8, 10), and in order to decrease the viscosity, which was still high in the octaester systems. Thus, while only the free-base derivative with octyl chains was mesomorphic (Cr 84 Col 891), all the metal complexes were mesomorphic (Figure 28), the mesophase decreasing in stability as the chains were elongated. " In all cases, the fluid mesophase was identified by optical microscopy as columnar. 

Zaleski and coworkers also prepared an interesting family of enediynes based on the porphyrin core [28]. These porphyrinic enediynes (Scheme 30.14) show systematic red shifts in their electronic spectra as a function of the number of conjugated alkyne units ( 13nm/alkyne), which indicate involvement of the enediyne units in the electronic excited states. Photochemical activation of the free base of tetraphenyl octakis(phenylethynyl) porphyrin derivative only led to the reduction of the porphyrin backbone via H-atom addition at the opposing me o-positions, suggesting significant activation barriers for the photo-BC. 

SCHEME 30.14 Reduction of the porphyrin backbone during photolysis of tetraphenyl octakis(j4ienylethynyl) porphyrin. 

The synthetic routes into p-trifluoromethylated corroles are significantly different from those used to prepare the p-fluorinated derivatives (Fig. 4). Direct trifiuoro-methylation of the p-position by halogen substitution in octabromocorroles was accomplished using Pd cross-coupling chemistry [37] identical to methodology used to isolate trifluoromethylated porphyrins (Scheme 14) [29,38]. The p-octakis-(trifluoromethyl)corrole was shown to be one the most electron-poor trivalent ligands ever reported for copper, as was gauged by cyclic voltammetry. 

Chen MJ, Fremgen DE, Rathke JW (1998) Oxygen atom transfer from p-oxo-bis[l,4,8,11,15,18,22,25-octakis(trifluoromethyl)phthalocyanmato]diiron(lll) evidence for an Fe =0 intermediate. J Porphyrins Phthalocyanines 2 473 82... 

Mashazi P, Antunes E, Nyokong T (2010) Probing electrochemical and electrocatalytic properties of cobalt(II) and manganese(lll) octakis(hexylthio) phthalocyanine as self-assembled monolayers. J Porphyrins Phthalocyanines 14(ll) 932-947... 

Yuan, Y., Gregg, B.A., Lawrence, M.F. lime-of-flight study of electrical charge mobilities in liquid-crystalline zinc octakis(beta -octoxyethyl) porphyrin films. J. Mater. Res. 15(11), 2494-2498 (2000). doi 10.1557/JMR.2000.0358... 

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