Porphin complexes

In Fig. 10 the proton NMR spectrum of cyanoferriporphin is compared to that of a diamagnetic porphin complex. In both spectra the protons... 

In order to increase the solubility of porphyrin and phthalocyanine complexes, several structural modifications have been made, a, jS, y, 6-Tetra-(4-pyridyl)-porphin complexes of copper(II), nickel(II), and zinc(II) have been synthesized (35) and their ultraviolet spectra determined in chloroform and in acid solution. By utilizing sulfonic acid groups to increase solubility, complexes of 4,4, 4",4" -tetrasulfophthalocyanine complexes of many metals were prepared (94j 95). This chelating agent was found to have a ligand field strength comparable to cyanide (94y 95). 

J.T. Groves, T. E. Nemo, R. S. Myers, Hydroxylation and epoxidation catalyzed by iron-porphine complexes-oxygen-transfer from iodosylbenzene, /. Am. Chem. Soc. 101 (1979) 1032. 

The simplest porphyrin, porphin (R, R = H and R = H), forms complexes with a variety of metal ions. It has 105(3 x 37-6) normal vibrations which are classified as shown in Table 111-9. Ogoshi et al. " prepared porphin complexes with Zn, Zn, Cu, and Ni, and carried out normal coordinate calculations... 

Table 111-9. Classification of Normal Vibrations OF A Metal Porphin Complex of D4,. Symmetry" ...

Ogoshi H, Watanbe E et al (1973) Synthesis and far-infrared spectra of ferric octaethyl-porphine complexes. J Am Chem Soc 95 2845-2849... 

Ard " and Gladkov and Solovyov propose, from normal coordinate calculations performed for the copper porphin complex, that bands near 368, 234 and 206 cm contain important contributions of the vCuN mode. From a vibrational study on the non-macrocycle phenantroline copper complexes it has been proposed the vCuN modes near 410 and 288 cm In bipyridine complexes of Cu(II), the vCuN mode is proposed at 297cm " a similar assignment is proposed in bipyrimidine complexes. ... 

The SERS spectral data obtained on colloidal Ag as well as Ag island films indicate a weak macrocycle interaction and small structural modifications of the naphthalocyanine complex on the surface. An energy transfer mechanism contribution to the observed enhancement was proposed. The whole spectral data point that the naphthalocyanine complex is oriented with the naphthalocyanine plane face-on to the surface. In both vanadylnaphthalocyanine and vanadylpor-phine tetraphenyl substituted complexes the vanadyl group is perpendicular to the coordination site and opposed to the surface. In both complexes the phenyl substituents, oriented perpendicular to the macrocycle plane, are responsible of the weak adsorbate-substrate interaction. Several different experimental conditions such as scanning speed, laser power and excitation lines wavelengths, concentration and metal surfaces were intended to obtain SERS of the porphine complex without success this was interpreted in terms that the complex has no interaction with the surface. Thus, it was concluded that the extension of the whole r-system plays a significant role in the mechanism involving the spectral enhancement by surface effect. 

Self-exchange rates of the three tetrakis-(4-pyridyl)porphine complexes [Fe(P)(imidazole)a] +/ +, [Fe(P)(OH)(OH2)] +/ +, and [Fe(P)(OHa)]6+/ + have been estimated as > 10 , > 10 , and 1.2 x 10 respectively. Of the iron(iii) complexes in this series, the first is low-spin, the second is believed to be an equilibrium mixture of high-spin and low-spin forms, and the third is high-spin. These results support a previous suggestion that electron transfer to or from a low-spin iron porphyrin system has a negligible Franck-Condon barrier. ... 

K.-J. Lin, Organometallic zeolite based on metal porphine complexes, (Academia Sinica, Taiwan). 2002, 99-342304... 

Whereas the great majority of aquo-chromium(m) complexes are inert to formation reactions, the tetra-(p-sulphonatophenyl)porphine complex is remarkably labile—stopped-flow techniques are required to monitor replacement of the co-ordinated waters of this complex by, for instance, chloride, cyanide, or pyridine. Analogous cobalt(in) complexes are also substitution labile. This has been attributed to the possibility of a redox mechanism for substitution. In view of the difficulty of reducing chro-mium(ni) to chromium(n) such a mechanism seems unlikely here, so that the porphine ligand may be promoting reactivity to substitution by electronic effects. ... 

The most dramatic example of non-leaving-ligand eifects in complexes of this type is provided by reactions of tetra-(A -methyltetrapyridyl)porphine complexes of cobalt(m). Here rates of substitution are several orders of magnitude faster than for the other cobalt(iii) complexes discussed in this section, ... 

The structure in Figure 24-24 is commonly found in both plant and animal matter. If the eight R groups are all H atoms, the molecule is called porphin. The central N atoms can give up their H atoms, and a metal atom can coordinate simultaneously with all four N atoms. The porphin is a tetradentate ligand for the central metal, and the metal-porphin complex is called a porphyrin. Specific porph Tins differ in their central metals and in the R groups on the porphin rings. 

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