Porphyrins and Related Complexes

Ruthenium and Osmium High Oxidation States S.6.4.4.9 Porphyrins and related complexes... 

However, there are a few true titanyl examples, mostly porphyrins and related complexes that do have Ti=0 bonds. The Ti=0 bond appears to be short 1.62 A while ir bands are in the region 890 to 972 cm 1 (Raman, v = 975 in 2 M HC1) consistent with a Ti=0 double bond. Octahedral titanyl complexes, such as (Me3tacn)Cl2TiO, are readily available from Tim precursors by oxidation with dioxygen in an aprotic solvent.17 A cationic titanyl complex which is stable in aqueous media18 can be made according to... 

This chapter gives an overview on the chemistry of tetravalent lanthanide compounds, especially those of tetravalent cerium. Following a brief introduction, it covers the tetrahalides, dioxides, and other lanthanides(IV) salts. Coordination compounds of cerium in the oxidation state +4 include halogeno complexes and complexes of oxo acids, /3-diketonates and related Schiff-base complexes, as well as porphyrinates and related complexes. 

Even flien well-characterized coordination compoimds are limited to only a few classes of compounds. Notable are, e.g., halogeno complexes and complexes of oxo acids, p-diketonates and related SchifF-base complexes, as well as porphyrinates and related complexes. Two other important classes of cerium(lV) compounds, the alkoxides and amides of Ce" +, can be regarded as pjewfifo-organometallics and are discnssed together with the organocerium(IV) complexes in Tetravalent Chemistry OrganometalUc. 

With their preference for square planar coordination, palladium(II) and platinum(II) are well suited to binding to porphyrins and related N4 donor macrocycles. Therefore, Pd(octaethylporphyrin) is readily synthesized starting from the labile PhCN complex (like the platinum analogue) [92]... 

It will not be lost on the reader that, while PHOTOFRIN and compounds (3), (5) and (6) contain no metal, they would be expected to be excellent ligands. Are metal complexes useful as PDT photosensitizers Indeed, they are, and may be expected in the future to become more important. The rest of this chapter is about this aspect it will emphasize metal complex formation and properties in relation to PDT. The synthesis of ligands, while of crucial importance, will not usually be treated here in detail, but leading references to relevant synthetic organic chemistry will be provided. The synthesis of porphyrins and related compounds has been considered in several monographs and reviews (porphyrins,46 47 phthalocyanines48). 

Table 2 contains redox potentials for representative porphyrin, SB, and related complexes in nonaqueous solvents. These data primarily illustrate the influence of axial ligation and porphyrin substituents on the Mn / potential. Planar macro-cyclic ligands such as phthalocyanine and corrole provide an equatorial coordination environment similar to that of porphyrins. 

Weiss, R. Gold, A. Trautwein, A. X. Terner, J. High-valent iron and manganese complexes of porphyrins and related macrocycles, The Porphyrin Handbook. Volume 4. Biochemistry and Binding Activation of Small Molecules , Eds. Kadish, . M. Smith, . M. Guilard, R. Academic Press San Diego, 2000, pp. 65-96. 

Complexes of acetylacetone (acacH), benzoylacetone (bzacH) and dipivaloylmethane (dpmH) have been reported. The acetylacetonate [Cr(acac)2] has been prepared from chromium(II) acetate and acetylacetone.142,143 It can also be obtained by the addition of aqueous sodium acetylacetonate to an aqueous solution of chromium(II) chloride, but in any preparation the yellow solid must be filtered off and dried as rapidly as possible, otherwise the chromium(III) compound is obtained. Its magnetic moment is 4.99 BM at room temperature consistent with a high-spin d4 configuration. 142The powerful reducing ability of [Cr(acac)2] has been used to prepare iron(II) and chromium(II) complexes80 of porphyrins and related ligands. 

Complexes with phthalocyanine, porphyrins and related macrocycles 271... 

Table 110 Selected Nickel(II) Complexes with Porphyrins and Related Systems... 

Zinc porphyrin complexes are also of interest in such photochemical systems, and photochemical studies of a series of porphyrin, porphine and related complexes have been... 

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