Porphyrin cores clusters

Besides the applications of the electrophilicity index mentioned in the review article [40], following recent applications and developments have been observed, including relationship between basicity and nucleophilicity [64], 3D-quantitative structure activity analysis [65], Quantitative Structure-Toxicity Relationship (QSTR) [66], redox potential [67,68], Woodward-Hoffmann rules [69], Michael-type reactions [70], Sn2 reactions [71], multiphilic descriptions [72], etc. Molecular systems include silylenes [73], heterocyclohexanones [74], pyrido-di-indoles [65], bipyridine [75], aromatic and heterocyclic sulfonamides [76], substituted nitrenes and phosphi-nidenes [77], first-row transition metal ions [67], triruthenium ring core structures [78], benzhydryl derivatives [79], multivalent superatoms [80], nitrobenzodifuroxan [70], dialkylpyridinium ions [81], dioxins [82], arsenosugars and thioarsenicals [83], dynamic properties of clusters and nanostructures [84], porphyrin compounds [85-87], and so on. 

Figure 14.5 Shielding of an iron porphyrin and thiolate cluster cores within dendrimers.

As with chromophores, the steric encapsulation of a dendrimer core can be utilized to prevent intermolecular interactions between redox active sites. A number of different redox active core moieties have been investigated, including, iron—sulfide clusters,9394 bis(terpyridine)iron(II) complexes,92 tris-(bipyridine)ruthenium(II) complexes,330 zinc porphyrins,252 oligothienylenevinylenes,331 fullerenes,236,332 ferrocenes,333-336 oligothiophenes,322 oligonaphtha-lenes,337 and 4,4 -bipyridinium.338... 

To date, iron-bound carbide occurs in molecular form only in strong-field carbonyl clusters, via CO reduction, and in porphyrin and porphyrin-like dimers,by reduction of tri- or tetrahalomethanes. In the biosynthesis of the FeMo-cofactor, carbide appears to come from the methyl group of S-ade-nosylmethionine, although the process by which it is converted to interstitial carbide remains unresolved. Available routes for carbide incorporation are therefore quite limited, and substantial synthetic development is probably necessary before Fe-C-S clusters can be realized. Alternative heteroligated Fe-Q-S cores, however, have been achieved. These efforts constitute necessary first steps toward the systematic construction of cofactor-relevant heteroligated cores. 

There has been considerable investigation of dendritic species with redox-active moieties placed at the center of the molecule. Various metal-polypyridyl complexes, as well as porphyrins and phthalocyanines, have been used as cores around which dendrimers have been built. Dendritic molecules with metallocenes at or near the core and dendrimers with central metal clusters have also been synthesized. In addition to metal complexes, electroactive organic moieties have been placed at the cores of various types of dendrimers. The rate of electron transfer between redox-active species and a working electrode, and... 

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