Dioxygen complexes spectroscopy

Iron dioxygen complexes, O NMR spectroscopy, 185 Iron-protoporphyrin IX... 

Infrared spectroscopy can be used to classify metal-dioxygen complexes as either superoxo species (p(O-O) from 1200 to 1070 cm-1) or as peroxo species (p(O-O) from 930 to 740 cm-1) (49). However, this system fails to accurately define the type of dioxygen species present in 8 and 15, as these complexes exhibit v(O-O) absorptions at 961 and 941 cm-1, respectively. Preparation of the complexes with 180-enriched dioxygen confirmed that the dioxygen was bound side-on (if) in these complexes Complex 8 exhibited isotopically shifted vibrations indicative of a side-on bound dioxygen 0(160-160) absorption at 961 cm-1, p(160-180) at 937 cm-1, and /(180-180) at 908 cm-1), as did complex... 

A trans-n- 1,2-Peroxo Dicopper(II) Complex. Our own efforts have resulted in the structural and spectroscopic characterization of five types of copper-dioxygen complexes (6), distinguished on the basis of the ligands used for their synthesis and on their distinctive structures or physical properties. Thus, the manner in which hemocyanin binds 02 is not the only one possible, and it is of considerable interest to deduce the structures, along with associated spectroscopy and reactivity of a variety of types. Dioxygen can bind to dinuclear transition metals in a variety of structural modes, shown in Figure 2. As mentioned, mode C is present in oxy-Hc and Kitajima s model complex (Scheme 1), whereas we have structural and spectroscopic evidence for types A (30-32), B (33-35), and F (36-38) for peroxo 022- binding, and mode D (39, 40) in the case of hydroperoxo (OOH ) complexes. 

The stoichiometric reaction of S02 with coordinated 02 to form coordinated sulfate appears to be general for dioxygen complexes. lsO isotope substitution and IR spectroscopy have been employed to study the reaction betwen [Ir(X)(CO)(02)(PPh3)2] (X = Cl, Br, I) and S02 (reaction 91). IR spectral results are consistent with a bidentate sulfate, ligand. The mechanism proposed for sulfate formation involves a peroxosulfate intermediate, that is insertion of S02 into one of the Ir —O bonds and bond formation between S and the leaving O, with subsequent rearrangement of the peroxo-sulfite intermediate thus generated (see Scheme 15).330,331... 

An > dioxygen complex has been prepared as an intermediate in the auto-oxidation of TP complexes, and E.P.R. evidence for such a species has come from studies of the auto-oxidation of Ti(TPP)F trapped in a matrix of Ti(TPP)0 ), however, in contrast with the T dioxygen complexes of cobalt, the spin density is only weakly localised on the dioxygen, and is quite high on the porphyrin ligand. E.P.R. spectroscopy has also been used to demonstrate an dioxygen species formed during the auto-oxidation of a Ti(III)... 

An early report of the formation of an rj dioxygen complex Co(CO)402 on sublimation of Co2(CO)g in the presence of dioxygen has been followed by studies with metal atom vapours which support the existence of Co(CO)402 and also suggest the formation of Co(CO)n02 (n = 1 to 3) in which the dioxygen appears from infra-red spectroscopy to form an complex. 

Electron Spin Resonance Spectroscopy. Practically all the ESR studies on dioxygen complexes have been concerned with 77 cobalt dioxygen complexes, and the results have been summarised in the review by Basolo et al. We limit our discussion here to the essential points relating to the electronic structure, and the reader is invited to consult the references given for fuller details. 

Mirica EM, Ottenwaelder X, Stack TDP. Structure and spectroscopy of copper-dioxygen complexes. Chem. Rev. 2004 104 1013-1045. 

Structure and spectroscopy of copper-dioxygen complexes with TV-heterocycles as ligands 04CRV1013. 

Gerothanassis, I. R, Momenteau, M. (1987). NMR spectroscopy as a tool for studying synthetic oxygen carriers related to biological systems Application to a synthetic single-face hindered iron porphyrin-dioxygen complex in solution, J. Am. Chem. Soc., 109 6944. 

Studies on the electronic spectroscopy of dioxygen complexes lead... 

As more dioxygen complexes were prepared and Raman spectroscopy became increasingly available, many new data were reported. Often the 0-0 vibration is infrared-inactive and can only be observed in Raman and Resonance Raman spectra. 

Infrared and Raman spectroscopy is perhaps the best method available for monitoring charge transfer to 0 in dioxygen complexes... 

O NMR spectroscopy is a potentially useful tool for investigating dioxygen complexes. In oxo-peroxo complexes of V, Mo and W, the resonance of the oxo group is detectable even in natural abundance. The observed chemical shift ranges are shown in Figure 3 [254]. 

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