Reaction-induced structural changes

Although the redox reactions in Sch. 12 have not been achieved electrochemically, they illustrate another type of redox-induced structural change in a dimolybdenum compound with a sulfur-rich coordination sphere. In this case, Mo2(/r-S)2 ring opening in 18 (cleavage of Mo—Mo and Mo—S bonds) is associated with the exposure of vacant coordination sites, and the uptake of two carbonyl ligands in 17 [7, 53]. 

An elegant example of the latter reaction was its application to peptide chemistry for inducing structural changes within the peptide chain. Peptide 23 readily cyclized to the 4-methylproline-containing derivative 24 in 64% yield (Sch. 15). The diastereoisomeric ratio was found as 2 1 in favor of the cis-isomer for this example. The Us-selectivity reflects the approach of the... 

Fluoride anion strongly interacts with various inorganic and organic boron and silicon compounds. These reactions are the basis for several fluoride sensors. Interaction of fluoride with boron compounds results in electron density redistribution and may also induce structural changes. Formation of fluoride complex by ferrocene derivative (Figure 16.19a) results in a decrease of oxidation potential by 200 mV... 

Stowell, M.H.B., McPhillips, T.M., Rees, D.C., Solitis, S.M., Abresch, E. and Feher, G. (1997) Light-induced structural changes in photosynthetic reaction center implications for mechanism of electron-proton transfer, Science (Washington, D. C.) 276, 812-816. 

High concentrations of heavy metals that affect, directly or indirectly, the redox potential in the reducing intracellular milieu, particularly copper, induce the formation of reactive oxygen species. These, in turn, can trigger the chain reaction causing lipid peroxidation, which affects membrane integrity and induces structural changes to proteins and nucleic acids that can result in cell death. 

Kleinfeld, D., Okamura, M. Y., and Feher, G., 1984, Electron transfer kinetics in photosynthetic reaction centres cooled to cryogenic temperatures in the charge-separated state evidence for light-induced structural changes. Biochemistry, 23 5780n5786. 

Kochi s book from 1978 [la] helped to establish electron-transfer and radical reactions as a crucial part of mainstream organometallic chemistry. The importance of such reactions is evident from Astruc s book [lb], still the most comprehensive and authoritative book in the area, and from several reviews and review collections [2] on aspects of organometallic electron-transfer reactivity. This chapter will be fully devoted to the use of electrochemical techniques to obtain bond-energy data for organometallic complexes, a topic that has not been previously reviewed. Aspects of the energetics of redox-induced structural changes and isomerizations, a thoroughly pursued topic, has been reviewed [2o] and will not be included here. 

Manogue and Katzer (284) have proposed that structure sensitivity that arises from reaction-induced surface changes rather than from the intrinsic properties of the underlying metal be called secondary structure sensitivity. For the oxidation of NH3 over Pt/Al203 (285), it was observed that small particles deactivated faster than did large particles, enhancing the original antipathetic structure sensitivity of this system. 

Stowell, M. H. B. McPhillips, T. M. Rees, D. C. Soltis, S. M. Abresch, E. Feher, G. "Light-Induced Structural Changes in Photosynthetic Reaction Center Implications for Mechanism of Electron-Proton Transfer,"5cience 1997, 276, 812-816. 

Changes in the hydrostatic pressure affect the reaction rates for molecularly dispersed species. In addition, pressure may affect the structure of the microemulsion in a way that significantly affects the rates of reaction. Changes in the fluid pressure can cause changes in the microstructure of the fluid, and the accessibility of the reactant to a catalyst will be altered. As indicated in previous sections, several different studies have shown that the density of the continuous-phase solvent can be used to induce structural changes in both the primary and secondary structures of the microemulsion. These structural changes can dramatically alter the reaction kinetics. 

Li ion usually occupies at the octahedron site, but it also m stay in a tetrahedron site and the Ni also is favor to occupy at tetrahedron site. Therefore if the disproportionate reaction is occurred and Ni can be formed, then the formed Ni may move to the tetrahedron site created by successive octahedra shown in figure 4. The or LF located at tetrahedron will increase the barriers of migrated Li+ ions and induce structural change from hexagonal to spinel structure as Fc304 shown in figure la. 

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