Ligation axial

THF solution [290]. There had been much confusion in the past about the magnetic moment of the iron(I) species and the correct Mossbauer and NMR properties caused by impurities of the samples and possible unknown axial ligation. However, with clean crystallized samples with known molecular structure [291], the first reduction product of iron(II)(tetraphenylporyphrin), [Fe(TPP)], can be clearly characterized as a quasiplanar iron(I) complex with spin S = 1/2 (EPR = 2.28,... 

Subsequent reaction of porphyrazines 170 and 171 with Cu(OAc)2 resulted in the selective metalation within the macrocyclic cavity to provide the corresponding copper complexes 166 (62%) and 172 (47%). Treatment of pz 170 with manganese acetate and iron sulfate in dimethyl sulfate gave the dmso adducts 173 (70%) and 174 (85%), respectively (168). Axial ligation was also observed when other metals were incorporated such as cobalt acetate, nickel acetate, and zinc acetate to give the metal complexes 175 (83%), 176 (70%), and 177 (90%) as the hydrates. The axial ligand of... 

Very recently, the kinetics and thermodynamics of a variety of axial ligation reactions have been investigated with Fe11 and Co11 porphyrins involving the small molecules CO, 02, and NO as ligands 27-30, 40, 92, 93). These experiments lead to the conclusion that the dynamic trans effects observed in these systems cannot alone be explained by the interaction models D and F (Fig. 1). Especially imidazole and its derivatives do not hold the place in various series of trans effects that they should take on the ground of their proton basicities. Therefore, besides their usual a-donor-tr-acceptor function, these unsaturated molecules are ascribed an additional 7r-donor function. 

Mutations of Cytochrome c that Affect Axial Ligation. 152... 

Protein-Conformation Effects on the Metal-Protein Linkage. Since we have been unable to find model Ni-porphyrin complexes whose Raman frequencies come close to those of the Ni-reconstituted proteins, it is clear that the protein matrix has an impressive effect on axial ligation. We might also ask what is the effect of changes in protein conformation on axial ligation. 

In addition, another weak line at 270gCm in natural abundance Mb shifts to 260 cm"" for the Ni protein (Figure 2). The weak 270-cm line may represent a fraction of the protein with a different state of axial ligation. Alternatively, another almost pure Ni-porphyrin vibration is a possibility. 

Excited State Axial Ligation Processes in Coordinating Solvents. 

Resonance Raman scattering provides a valuable method of determining the state of axial ligation in nickel-reconstituted heme proteins and Ni-porphyrin complexes. A pattern of shifts in the Raman coresize and oxidation-state marker lines can be used to monitor changes in axial coordination. The shifts in the core-size lines (e.g. indicate an expansion of the core from about 1.96 A for the 4-coordinate Ni porphyrin to 2.04 A for the 6-coordinate species,... 

The spectra presented in Figures 1-3 demonstrate that high quality, transient resonance Raman spectra can be obtained for Ni(OEP) and Ni(PP) solutions using Soret excitation. These spectra can be interpreted on a molecular level by comparison with the extensive theoretical and experimental data base that exists for ground state nickel porphyrin species (8-16 and refs, therein). The coordination state of nickel porphyrins can easily be detetmined from the resonance Raman spectrum of the sample (10.12). Several modes in the Raman spectrum of porphyrins are quite sensitive to the state of axial ligation (10.12). In particular, the marker lines V4, 11 2> 3 10 (porphyrin skeletal mode designations follow those of Abe et al., (I2a). The designation... 

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