Lead complexes porphyrins

Porphyrin, octaethyl-, lead complex cyclic voltammetry, 4, 399 <73JA5140)... 

The dication [(oep)Pb(IV)]2+ is unstable. Its absorption spectrum differs from that of doubly oxidized porphyrins of other metals like Zn or Mg, where the ligand is doubly oxidized. Spectrometry and voltammetry indicate that PblV binds weakly to the unoxidized ligand (the Soret and adjacent lines are those of the unoxidized ligand). Another unique aspect of the lead complex is its instability, which stands in contrast to the stable Sn(IV) analog171, implying the inability of PblV to accommodate into the central cavity of the porphyrin plane. 

The synthesis of lead(II) porphyrin complexes has been efficiently performed in a solid-state reaction. Grinding together equimolar amounts of (por)H2 (porH2 = meso-(4-HO-C6H4)4-porphyrin, meso-(4-MeOC6H4)4-porphyrin, or meso-(4-N02-C6H4)4-porphyrin) with lead(II) acetate in a pestle and mortar with a trace of acetone leads to the (por)Pb complexes in excellent yield after chromatographic purification. ... 

Only one sequence of a complex porphyrin synthesis is described here, namely the path leading from a P-substituted porphyrin to a chlorine containing... 

The effect of the metal ion was investigated, too (Figure 27). Except for the lead complex, all complexes showed an enantiotropic, columnar mesophase characterized as Coh by miscibility studies with the zinc complex. As for the phthalocyanines, the lead ion was located out of the porphyrin plane but here, this distortion and the consequent disturbance of the tt stacking led to total suppression of the mesophase. The transition temperatures were similar for all mesomorphic metal complexes, with a perceptible effect of the metal on the clearing temperatures, which... 

The electrochemistry of (P)Ge(R)2 and (P)Ge(R)X are characterized by one or two reversible single-electron additions leading to porphyrin r-anion radicals and dianions. The compounds also undergo two oxidations, the first of which is always reversible in the case of the (P)Ge(R)2 complexes [58]. A rapid cleavage of the Ge-carbon bond was proposed to follow electron transfer and the final product of the oxidation was formulated as (P)Ge(R)(Cl04) [58]. 

Thermal Lensing, Detection, Figure 8 Performance of TLM for ultrasensitive detection of molecules. The sample was lead(ll)-porphyrine complex solution... 

Thallium(III) acetate reacts with alkenes to give 1,2-diol derivatives (see p. 128) while thallium(III) nitrate leads mostly to rearranged carbonyl compounds via organothallium compounds (E.C. Taylor, 1970, 1976 R.J. Ouelette, 1973 W. Rotermund, 1975 R. Criegee, 1979). Very useful reactions in complex syntheses have been those with olefins and ketones (see p. 136) containing conjugated aromatic substituents, e.g. porphyrins (G. W. Kenner, 1973 K.M. Smith, 1975). 

Reaction of [Rh(CO)2Cl]2 with porphyrins (e.g. H2TPP) leads to Rh(por-phyrin)(CO)Cl, which readily lose CO. Some of the chemistry of the octaethylporphyrin complexes [102] is shown in Figures 2.51 and 2.52. 

Oyaizu K, Haryono A, Natori J, Shinoda H, Tsuchida E. 2000. Electroreduction of /r-oxo iron(III) porphyrins adsorbed on an electrode leading to a cofacial geometry for the iron(ii) complex Unexpected active site for the catalytic reduction of O2 to H2O. Bull Chem Soc Jpn 73 1153. 

The ligand group can be introduced either on the meso or on the /5-pyrrole position of the porphyrin ring, but the synthesis of the meso-functionalized derivatives is easier and has been more widely exploited. Balch (50-53) reported that the insertion of trivalent ions such as Fe(III) (32) and Mn(III) (33) into octaethyl porphyrins functionalized at one meso position with a hydroxy group (oxophlorins) leads to the formation of a dimeric head-to-tail complex in solution (Fig. 11a) (50,51). An X-ray crystal structure was obtained for the analogous In(III) complex (34), and this confirmed the head-to-tail geometry that the authors inferred for the other dimers in solution (53) (Fig. lib). The dimers are stable in chloroform but open on addition of protic acids or pyridine (52). The Fe(III) octaethyloxophlorin dimer (52) is easily oxidized by silver salts. The one-electron oxidation is more favorable than for the corresponding monomer or p-oxo dimer, presumably because of the close interaction of the 7r-systems in the self-assembled dimer. 

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