Heme iron complex

Cyclopentene-l-dithiocarboxylic acid, 2-amino-meta complexes, 2, 800 Cyclophane chlorophylls, 3, 58 Cyclophane hemes iron complexes, 4,1269 Cyclophosphazenes metal complexes, 2, 81 Cyclopropane carbonylation... 

The stepwise oxidation of alkylamine, which leads to N-dealkylation, generates nitrones that form tightly bound complexes with the heme iron [48]. These heme iron complexes give rise to characteristic changes in the UV-Vis spectrum of the CYP. 

Vanin, A. F., and Varich, V. Y. (1981). Nitrosyl non-heme iron complexes in animal tissues. Stud. Biophys. 86, 177-185. 

The antitumor antibiotic bleomycin (BLM) is believed to cause cytotoxicity through its ability, in the combined presence of dioxygen and a metal ion cofactor (204), to bind to and degrade DNA (205). Iron complexes of BLM have aroused special attention, as such complexes are the first (vide supra concerning the discussion of hemerythrin and hemocyanin) non-heme-iron complexes with a significant capacity for dioxygen activation (206). 

Non-heme Iron Complexes with Tetra- and Pentadentate Ligands... 

Two examples of non-heme iron complexes with tetradentate ligands should be presented, illustrating the problems associated with the use of such complexes for synthetic purposes. 

Clearly, while porphyrin complexes are obvious candidates for modelling these kinds of biomimetic oxidations, a range of non-heme iron complexes based on macrocyclic and podand ligand have also proved to be successful structural and functional mimics.19 To take one example, Figure 12.13 shows the X-ray structure of the iron (IV) tetramethylcyclam (tmc) oxo complex [Felv(tmc)(0)(MeCN)]2+... 

Olefin aziridination catalysts derived from other transition metals continue to be developed. Simple non-heme iron complexes have been reported to serve as effective... 

M. Klopstra, G. Roelfes, R. Hage, R. M. Kellogg, B. L. Feringa, Non-heme iron complexes for stereoselective oxidation Tuning of the selectivity in dihydroxylation using different solvents, Eur. J. Inorg. Chem. (2004) 846. 

G. Roelfes, V. Vrajmasu, K. Chen, R. Y. N. Ho, J.-U. Rohde, C. Zondervan, R. M. la Crois, E. P. Schudde, M. Lutz, A. L. Spek, R. Hage, B. L. Feringa, E. Miinck, L. Que, Jr., End-on and side-on peroxo derivatives of non-heme iron complexes with pentadentate ligands Models for putative intermediates in biological iron/dioxygen chemistry, Inorg. Chem. 42 (2003) 2639. 

There are few peroxide adducts of synthetic non-heme iron complexes that are well characterized (Table VI). Perhaps the best known adduct is that derived from Fe (EDTA) under basic conditions. This purple complex has an absorption maximum near 520 nm (e 528 M cm ) (163). These are absorptions characteristics associated with the peroxide-to-Fe" charge-transfer band in oxyHr however, the coordination mode of peroxide in the complex appears to be different from that in oxyFIr. After some debate in the literature, it has been concluded that the peroxide is T --bound on the basis of isotope effects observed in the Raman spectrum of the complex (158, 164). The v(O-O) of the H2 Oi complex is found at 815 cm". When is used, the v(O-O) shifts to 794 cm and appears as a peak of comparable line width. Were the peroxide only ri -bound, two peaks due to the Fe-O -O " and the Fe-" 0- 0 isotopomers would have been expected, as in oxyHr. An ri -peroxo structure is also proposed for [Fe(TPP)02] and has been determined for the corresponding [Mn(TPP)Oi] complex (165). 

In the last few years, several non-heme iron complexes have been identified as functional models for non-heme iron dioxygenases (85-88). These model complexes are able to catalyze the cis-dihydroxylation of olefins as well as the epoxidation of olefins using H2O2 as the primary oxidant. Table V presents the results of olefin oxidation by some representative mononuclear and dinuclear non-heme iron complexes in combination with H2O2. 

Catalysis of Olefin Oxidation by Some Representative Mononuclear and Dinuclear Non-Heme Iron Complexes in Using H2O2 as Oxidant... 

Fig. 15. Non-heme iron complexes as models for naphthalene 1,2-dioxygenase (88).

With regard to the biomimetic non-heme iron complexes, the work devoted to develop catalysts that perform catalytic alkane hydroxylation has resulted in a large number of iron complexes, which generate Fe =0 iron-oxo species characterized by different spectroscopic techniques. There is now direct evidence that the involvement of high-valent iron-oxo species leads to stereospecific alkane hydroxylation, while hydroxyl radicals contribute to non-selective oxidations. The impressive work performed by Que and co-workers has demonstrated that olefin epoxidation and cis-dihydroxylation are different facets of the reactivity of a common Fe -OOH intermediate, whose spin state can be modulated by the electronic and steric properties of... 

Because of the success with iron cyclam, our search for other non-heme iron complexes involved a survey of cyclam like ligands including HMCD (5,7,7,12,14,14-hexamethyl-l,4,8,ll-tetraazocyclodec-4,l 1-diene), TIM (2,4,9,10-tetramethyl-l,4,8,ll-tetraazocyclodec-l,3,8,ll-tetraene), TDO (1,4,8,ll-tetraazocyclodecane-5,7-dione), etc. Under the same reaction conditions as for iron cyclam, the iron complexes of these other ligands also proved to be efficient catalysts for olefin epoxidation with PhIO and MCPBA, but not for H2O2. These results further support the notion that the three oxidants behave differently in their reactions with these non-heme iron complexes. 

Figure 2-27. Structure of the reaction center complex of Rps.viridis. a) Whole structure, b) Prosthetic groups extracted from the whole structure (He = heme iron complex).

Reginato N, McCrory CTC et al (1999) Synthesis, X-ray crystal structure, and solution behavior of Fe (NO)2 (1-Melm)2 implications for nitrosyl non-heme-iron complexes with g = 2.03. J Am Chem Soc 121 10217-10218... 

We envisioned that at higher 1-MeIm concentration the hyponitrite hgand may be displaced in which case the EPR active (OEP)Fe(l-MeIm)2 complex could form. Quite interestingly, the latter complex was not observed in the EPR spectrum. Thus, it is likely that the presence of the N-donor histidine at the axial position of the heme iron complex may play a role in speeding up the rate of reduction of NO to N2O in NORs. 

Hgure 6 ESR spectra of liver tissue from mice at 77 K (A) control animal on normal diet (B) mouse on drinking water with 0.3% nitrite for 7 days. The nitrite consumption induces formation of dinitrosyl-iron (DNIC 0.03) and nitrosyl-heme complexes, at g=1.98. (Reproduced with permission from Varich V (1979) Changes in amounts of dinitrosyl non-heme iron complexes in animal tissues depending on animal growth. Biofyzika (Russian) 24 344-347.)... 

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