Chlorine complexes

The complex with the reduced porphyrin derivative 5,10,15,20-tetramethylisobacteriochlorin, [Ni(TMiBC)] (688), has an -ruffled conformation and a bond length pattern indicative of a reduction of aromaticity, both of which are more pronounced than those found for the corresponding porphyrin and chlorin complexes.1786... 

These are therefore some mechanisms for the development of chlorine complexes and the continued supply chain of chlorine through the derivatives. These also allow the increased use of HCl in the system and some control of the caustic supply. 

Iron chlorin complexes have been studied by resonance Raman spectroscopy. Observations have predictive value, and offer criteria for an identification of metallochlorin prothetic groups in biological systems (85JA182). 

In syntheses of meso-tetraalkylchlorins, problems arise with contamination by chlorins. A template synthesis was described wherein the ratio of porphyrin and chlorin complexes formed can be controlled by the metal and the amount of the anhydride used (Scheme 5). Demetallation of complexes was... 

Each of the photosystems ejects an electron from the excited chlorin complex to a quinone within a nanosecond, followed by electron transfer along chains leading out of the charge separation center within 100 ns. The high potential reaction of Tyr and Mn in PSII is quite rapid, beginning in the simulations on the same time scale as the quinone reduction reaction. However, it has been suggested that tyrosine oxidation may not be rate limited by tunneling, but by H+ transfer (Diner et al., 2001). 

According to Tsao et al. [62], three possible structures of benzene-chlorine complex were obtained (Figure 13.1). The first one is high symmetric C(,v) hexahapto-complex with chlorine atom over the centre of the benzene ring (Figure 13.1a), which was firstly proposed by Russel [63]. The second and third structures had Cs symmetry the chlorine atom was located over the carbon-hydrogen bond... 

FIGURE 13.1 Structures of benzene-chlorine complexes, (A) C v symmetric complex, (B) p-complex, (C) s-complex. 

TABLE 13.1 Relative energy, enthalpy and free energy (kcal/mol), and equilibrium constants (cmVnnolecule) of benzene-chlorine complexes, transition state and products of benzene-chlorine reaction... 

TABLE 13J Relative energy, enthalpy and free energy (kcal/mol) of toluene-chlorine complexes... 

The 5,10,15,20-tetraphenyl-21H,23H-porphyrin, or m o-tetraphenylpor-phyrin (TPPH2), employed is prepared by a general method for condensing weio-porphyrins, and its properties are described elsewhere (it can now be obtained cheaply from various chemical suppliers, e.g., Strem and Aldrich). If the starting material is not chlorin-free, the copper-chlorin complex will be removed in the chromatographic purification therefore purification of the... 

If a chlorine complex of thioanisole is used to open oxiranes, a-chlorocarbonyl derivatives may be synthesized in a single step (Eq. 323). ... 

Key a, spectrum ofnickel porphyrin fraction b, spectrum typical of Samples 3,61,421, and 441 and identified as vanadyl porphyrins c, spectrum typical of Samples 422 and 4422, tentatively identified as vanadyl phylloerythrin derivatives and d, spectrum of Sample 630 possibly a vanadyl-chlorin complex. This sample contained some vanadyl porphyrin impurities as shown by the absorption peaks at 407, 575, and533 nm. 

Radiolysis of CCI4 solutions has been shown to lead to one-electron oxidation of many solutes. While the detailed mechanisms of the radiolysis of this solvent have been under study by several groups and some contradictory conclusions have been drawn, it is certain that many compounds are readily oxidized in this solvent. Oxidation may be effected by solvent or fragment cations, by chlorine atoms or chlorine complexes and. 

However, the interpretation of Ru(I) species being the products of the transformation is not very plausible, since the CO-stretching frequency of the resulting species is closer to the parent complex than the primary radical anions. Another study revealed that the radical anionic [(TPP)Ru(CO)(THF)] readily undergoes formation of the corresponding chlorine complex in the presence of MeL Such electrophilic attack might also be the reason for the above-described transformations in protic or highly polar media. 

Fig. 14. Experimental and theoretical Mossbauer spectra of ferric chloroperoxidase and its halide complexes, (a) Native chloroperoxidase, pH 3, T = 4.2 °K, Ho = 1.3 kOe, o J. y- An identical spectrum was found for the chlorine-complex measured under the same conditions, (b) Iodine complex, pH 3, T = 1.5 °K, Ho = 1,3 kOe, Hq f. (c) Fluoride complex, pH 3, T = 4.2°K, Ho = 1.3 kOe, [Taken...

Rosell and Svennson (1975) described a procedure whereby a methylated polysaccharide that contained a limited number of free hydroxyls at specific positions could be selectively degraded. Using a dimethyl-sulfoxide-chlorine complex (Corey and Kim, 1973), the free hydroxyls are oxidized to keto (or aldehyde) groups. Treatment of the oxidized material with base results in the elimination of glycosyl or methoxyl substituents 3 to the activated group, and the resultant a,p-unsaturated... 

Ozawa, S., Y. Watanabe, and 1. Morishima (1994). Spectroscopic characterization of peroxo-iron(Ill) chlorin complexes. The first model for a reaction intermediate of cytochrome d. Inorg. Chem. 33, 306-313. 

An even more stringent test is represented by CT complexes, and in particular those arising from a n-a type interaction, such as that of ethylene with a halogen molecule. These systems are very difficult to describe either at the post-HF and DF levels. Among the well characterized CT systems, we have focussed our attention on the simple ethylene-chlorine complex. Furthermore, even if several possibile molecular arrangements are possible, the axial-perpendicular structure is the most stable one. So we have limited our attention only to this molecular arrangement, whose main molecular parameters are reported in table IX. 

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