Porphyrin-type compounds

Based on elemental analyses and microprobe tracing (Dautzenberg et al., 1978), metal deposits appear to be present in sulfide forms and not as adsorbed porphyrin-type compounds or as metals in the elemental or metallic state. Takatsuka et al. (1979) and Rankel and Rollmann (1983) have reported direct linear correlations of the spent catalyst sulfur content with the deposited metal content. The sulfide forms of nickel and vanadium are consistent with expectations based on thermodynamics for the conditions typically encountered in residuum hydroprocessing units (600-800°F, 1000-2200 psig, H2/H2S environment). 

Attempts to demetallate the various porphyrin fractions appeared partly successful only in the case of the nickel porphyrins and for sample 3, while demetallation of samples 630, 422 and 4422 yielded no porphyrin type compounds at all. HPLC runs on the demetallated nickel porphyrins and the vanadium porphyrins from fraction 3 showed these to be significantly different. Similar observations have been made previously (12) and may explain why the nickel and vanadium porphyrins appear to have different distributions in the drill cores. However,... 

The divinyl porphyrin dimer ether examined by Morris and Ward [57] and Pandey et al. [15] (Figure 20) also appears to be more efficient and less retained in the skin than are Hpd and Photofrin. Unfortunately, these compounds offer little improvement in photophysical properties over Photofrin, with low absorbences in the near red spectrum and in general are much more difficult to prepare and purify. Further development of porphyrin type compounds for clinical PDT is therefore unlikely in view of several promising compounds with more advantageous photophysical properties. 

We have shown that the reversible oxygen uptake of myoglobin and hemoglobin is very sensitive to the kind and sequence of a-amino acids in the macromolecular protein chain. Now it is interesting to speculate if it is possible to substitute the heme in, for example, myoglobin by other porphyrin-type compounds without loss of reversible oxygen function. This topic forms a bridge between fully natural and fully artificial/synthetic systems. 

Dispersion of Porphyrin-Type Compounds in Different Organic Polymers and Photoelectrochemical Oxygen Reduction (Section 8.2.1) [14,15]... 

Given stringent requirements for effective sensitizers and the desire to use wavelengths further to the red for therapeutic appHcations, definition of newer sensitizers has been a principal area of research since about 1987. Expanded theoretical and experimental understanding of photophysics has been a key element in identifying new classes of potential sensitizers (93—98). Research has focused on cationic derivatives of Nile Blue (93), metaHo-phthalocyanines (94), naphthalocyanines (95), chlorin-type compounds (96), expanded ring porphyrinoids (97), as well as porphyrins other than hematoporphyrin and its derivatives (98). This work has also been reviewed (10,91). Instmmentation for photodynamic therapy has been reviewed (99). 

There are, however, some crown type compounds which contain no structural feature except the thiophene subunit, and these deserve some comment here. This is especially true since one of these compounds was prepared very early in the history of crown compounds. Ahmed and Meth-Cohn were interested in sulfur analogs of the porphyrin ring system and prepared compound 7 in 1969 by the method shown in Eq. 

Fig. 9. Reaction of ChBNiPr with the dilithiated di-2-thienylhorane amine 27 gives the tetrathiaporphyrinogen 28. Compound 29 is a porphyrin-type macrocycle...

Dendrimers built around a metal complex as a core. These compounds can be considered metal complexes of ligands carrying dendritic substituents (Fig. 1 a). The most commonly used metal complex cores are porphyrin complexes, polypyridine complexes, and ferrocene-type compounds. 

Despite the many model compounds that have been prepared, picket fence porphyrin and its many cogeners, first reported by the CoUman research group in 1974, remains the only porphyrin-type ligand system yielding... 

Cobalt complexes with square planar tetradentate ligands, including salen, cor-rin, and porphyrin types, all catalyse the reduction of alkyl bromides and iodides. Most preparative and mechanistic work with these reactions has used cobalamines, including vitamin-B,. A generalised catalytic cycle is depicted in Scheme 4.10 [219]. At potentials around -0.9 V vs. see, the parent ligated Co(lll) compound un-... 

Kong and Loach [30, 31] were the first to synthesize porphyrin-quinone compounds of the P-L-Q type. The structure of the compounds they obtained (n — 2, 3) is shown in Fig. 8(a). A strong quenching of the fluorescence of the... 

Liu prepared a sandwich type coordination compound (103) from porphyrin and phthalocyanine with the assistance of a microwave. The resulted compounds showed good solubility in conventional organic solvents. The photoelectric conversion properties have been tested with a Gratzel type cell. The results revealed that the sandwich type compound showed better photo-electric conversion efficiency than the corresponding monomeric porphyrin or phthalocyanine precursors. The short-circuit photocurrent of the solar cell with this sandwich type compound as sensitizer, was, as high as 691.31 A cm-2, which was much better, than those of porphyrin or phthalocyanine monomers [100]. 

Finally porphyrins and phthalocyanins can give sandwich type compounds such as UIV(porph)2, UIV(Pc)2, and [UnI(porph)2]. 32 Thorium gives similar complexes. 

Multi-ferrocenyl phthalocyanines having up to 16 ferrocene units per molecule have been built with oxyethylene linkers to create aliphatically linked ferrocene units, and ethynyl bridges have been used to create ferrocenyl-linked tetrapyrroles of both phthalocyanine and porphyrin types with unsaturated links the porphyrins have two ferrocene units, which are placed on opposite meso positions. Both the aliphatically linked and the ethynyl-linked compounds were shown to exhibit no electrochemical communication between ferrocene units. ... 

It is of interest that when aluminum porphyrin is used, oligomers or polymers of controlled molecular weight distribution can be produced by using bisphenol A or related bisphenol-type compounds as chain transfer agents. 

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