Magnetic interactions between

We will use here the main results obtained for two complex and distinct situations the structural and spectroscopic information gathered for D. gigas [NiFe] hydrogenase and AOR, in order to discuss relevant aspects related to magnetic interaction between the redox centers, intramolecular electron transfer, and, finally, interaction with other redox partners in direct relation with intermolecular electron transfer and processing of substrates to products. 

Foumel, A., Gambarelli, S., Guigliarelli, B., More, C., Asso, M., Chouteau, G., Hille, R., and Bertrand, P. 1998. Magnetic interactions between a 4Fe-4S l+ cluster and a flavin mononucleotide radical in the enzyme trimethylamine dehydrogenase a high-field electron paramagnetic resonance study. Journal of Chemical Physics 109 10905-10913. 

Anisotropic exchange interaction within the Lines model described above. Dipole-dipole magnetic interaction between centres is calculated fully ah initio and is added to the exchange matrix. 

In order to understand the nature of mixed-valent compounds one must consider both electrostatic and magnetic interactions between centres which have different oxidation states. Nevertheless, as schematically shown in Figure 14, simple electrostatic effects can help to clarify the so-called Robin-Day classification.24 This is based on the degree of electronic delocalization in (usually binuclear) mixed-valent compounds. 

Magnetic susceptibihty measurements [256] on Cu VCo VZn/Al LDHs indicate that the Cmie-Weiss law is obeyed with a Weiss temperature close to zero, indicating the lack of magnetic interactions between paramagnetic ions and thus a random distribution in the lattice. It has been proposed, however, that the catalytic activity of Mg Al LDHs n = 2,3) containing interlayer carbonate anions in the oxyethylation of 1-dodecanol with ethylene oxide can be correlated with the distance between AP" cations in ordered lattices [250]. 

Tetraneopentyl zirconium reacts in the same way as tetraneopentyl titanium to give, on a silica (soo), a tris(neopentyl) monografted species [32]. Treatment under H2 of this surface species yields silica-supported zirconium hydrides [33], which have been characterized as a mixture of mono- (65-70%) and bis- (35-30%) hydrides based on double quanta NMR experiments (Scheme 2.11) [34]. Interestingly, the double quantum experiment allows us to prove not only the presence of the two hydrides and the monohydride of zirconium by the presence or the absence of the double quanta correlation but also to detect the through space magnetic interaction between the zirconium monohydride and the silicon di-hydride, proving thus the spatial arrangement on the surface. This confirms the mechanism by which these hydrides have been formed on the surface. 

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