Tetra porphyrin ligand

The reaction of the porphyrin ligand, TTP (tetra-p-tolylporphyrin) with BF3-OEt2 leads to the oxide fluoride complex, B2OF2(TTP) and the structure has been established using H, 13C, nB and 19F NMR spectroscopy and FAB mass spectrometry [9], The structure contains a B—O—B bridge in which each boron is bonded to fluorine and to a nitrogen of TTP. The structure of the diboron complex was confirmed by an X-ray crystal structure determination of the tetrakis-(p-chlorophenyl)porphyrin (TpCiPP) derivative. 

The presence of this and other materials presents potential problems in industrial processing, and there is great interest in characterization of the chemical nature of the vanadium species present. EPR is most widely used in these studies since the metal is in the oxo-vanadium(IV) state. Optical spectroscopy in the visible region can also be used on extracts since oxo-vanadium(IV) porphyrins, which absorb at around 572 nm and 534 nm 116,119), can readily be detected. However, it has been shown (120-122) that the total amount of vanadium present in crude oils and tar sand bitumen is higher than can be accounted for by the presence of oxo-vanadium(IV) porphyrins. It has therefore been suggested that the vanadyl may be bound to a range of different tetra-dentate ligands in crude oils (120-123). 

Other important tetra-azamacrocycle ligands displaying interesting electrochemistry particularly with metals of the iron group are phthalocyanines, porphyrins, and related species. We now discuss two examples of catalytic small molecule reduction by iron-porphyrin catalyst. 

The above studies were later extended to the controlled polymerization of AA in water at 333 K to produce well-controlled PAA chains by use of the water-soluble Co complex IV with the tetra(3,5-disulfonatomesityl)porphyrin ligand. For instance, a 81.6% conversion in 30 min, including... 

Classic A/-heterocychc ligands, eg, bipyridyl (bipy), terpyridyl, imidazole, pyrazine, phenanthroline, piperazine (including alkyl- and aryl-substituted derivatives), and polypyrazol-l-yl-borates (bis, tris, and tetra), have all been found to coordinate Th(IV) chlorides, perchlorates, and nitrates. The tripodal hydrotris(pyrazolyl)borates, HBPz, have been used to stabilize organometaHic complexes (31). Bis-porphyrin Th(IV) "sandwich" complexes have been... 

The reduction electrochemistry of ECP porphyrin films furthermore responds to added axial ligands in the expected ways. We have tested this (2,6) for the ECP form of the iron complex of tetra(o-amino)phenyl)porphyrin by adding chloride and various nitrogeneous bases to the contacting solutions, observing the Fe(III/II) wave shift to expected potentials based on the monomer behavior in solution. This is additional evidence that the essential porphyrin structure is preserved during the oxidation of the monomer and its incorporation into a polymeric film. 

Ni2+ was very popular in the early days of the investigation of mechanisms of complex formation, since the time-scale for its reactions with simple ligands was so convenient for the then recently developed stopped-flow technique. However, interest has now moved on to other first-row cations, especially to Cu2+. A review of the kinetics and mechanisms of formation of tetraazamacrocyclic complexes concentrates on Ni2+ and Cu2+, and their reactions with cyclam and similar ligands (267). The tetra(4 -sulfonatophenyl)porphyrin complexes of Ni2+ and of Cu2+ react immeasurably slowly with cyanide, but their IV-methyl derivatives do react, albeit extremely slowly. The relevant time scales are hours for removal of Ni2+, months for the removal of Cu2+, by 10-4 M cyanide at pH 7.4 (268). 

However, the d6 metalloporphyrins specified in Series b and c (Table 17) allow a combined interpretation of data pertinent to the porphyrin, the metal, and the axial ligand if the latter is a w-acceptor. A hypsochromic shift of the (3-band in the tetra-arylporphyrins and the a-band in the octaethylporphyrins occurs in the series Fe <... 

In the case of manganese porphyrin catalyzed epoxidations, the axial ligands have been used alone or together with other additives like carboxylic acids (Banfi and coworkers) and soluble bases (Johnstone and coworkers). For example, Mansny and coworkers showed that in the presence of imidazole, 2-methylimidazole or 4-imidazole chloromanganese(tetra-2,6-dichlorophenylporphyrin) catalyzes the epoxidation of varions aUtenes including 1-alkenes by Under these conditions alkene conversion... 

In this section we will consider several complexes. The particular systems that were investigated are composed of a central metal ion M (M=Zn2+, Mg2+, or Ni2+) with porphyrin (P), tetra-phenylporphyrin (TPP), tetraazoporphyrin (TAP), or phthalocya-nine (Pc) as the ligand. The absorption and MCD spectra of the porphyrin and TPP complexes are sufficiently similar to each other that they can be discussed together. The review of the TAP and Pc results will be presented later. 

Complexes with tetradentate ligands L (L = (salen)2-, (acacen)2-), of the form [MoCl2L], have been prepared by reaction of [MoCl4(NCMe)2] or [MoCl3(py)3] with H2L.159 The reaction of HC1 with [MoO(TPP)] (TPP = dianion of 5,10,15,20-tetra-4-tolylporphyrin) forms [MoCl2(TPP)] the structure of the latter involves a planar porphyrin ring with the tram chlorides at distances from the molybdenum of 2.347(4) and 2.276(4) A, although they appear to be chemically equivalent.113... 

---