Delocalization in mixed valence

Sherman, D.M. (1985) Electronic structures of Ee " coordination sites in iron oxides application to spectra, bonding and magnetism. Phys. Chem. Min. 12 161-175 Sherman, D.M. (1987). Molecular orbital (SCF-Xa-SW) theory of metal-metal charge transfer processes in minerals I. Application to the Fe vpe charge transfer and electron delocalization in mixed-valenced iron oxides and si-licates.Phys Chem Min 70 1262-1269 Sherman, D.M. (1990) Crystal chemistry, electronic structure and spectra of Fe sites in clay minerals. Applications to photochemistry and electron transport. In Coyne, L.M. McKeever, S.W.S. Blake, D.F. (eds.) Spectroscopic characterization of minerals and their surfaces. A.C.S. Symposium Series 415, 284-309... 

In most instances, the magnetic structure of a compound can be understood to be based on interacting localized spin centers, such as classical 3d/4d/5d transition metal ions and 4f lanthanide or 5f actinide cations with unpaired electrons. Note that while the assumption of localized moments is valid for many compounds comprising such spin centers, even partial electron delocalization in mixed-valence coordination compounds renders many localized spin models inapplicable. 

Sherman, D. M. (1987a) Molecular orbital (SCF-Xa-SW) theory of metal-metal charge transfer processes in minerals. I. Applications to Fe2+ -+ Fe3 charge transfer and electron delocalization in mixed-valence iron oxides and silicates. Phys. Chem. Minerals, 14, 355-64. 

Spin Coupling and Electron Delocalization in Mixed-Valence Iron—Sulfur Clusters... 

The present work was undertaken in order to define more exactly the processes of electron delocalization in mixed valence heteropoly anions. The work has also proved the existence of geometric isomers that result from the various ways of arranging two kinds of metal atoms within a given structure (5, 6). 

As first shown by Boxer et al. electroabsorption (or Stark effect) spectroscopy provides an experimental method to determine the extent of delocalization in mixed-valence complexes. Unfortunately, the technique is experimentally very difficult and this has limited its application. Nevertheless, Stark effect measurements of parallel and orthogonal intervalence transitions in... 

Gamelin, D. R., Bominaar, E. L., Mathoniere, C., Kirk, M. L., Wieghardt, K., Girerd, J. J., Solomon, E. I. Excited-state distortions and electron delocalization in mixed-valence dimers Vibronic analysis of the near-IR absorption and resonance Raman profiles of [Fe-2(OH)(3)(tmtacn)(2)](2-i-). Inorg Chem 1996, 35, 4323 335. 

Multimode Jahn-Teller Problem in Mixed-Valence Trimers Vibronic Localization-Delocalization... 

The [Fe3S4] complex occurs naturally in a completely oxidized (3Fe ) and mixed Fe /Fe oxidation states. Fully reduced forms of the three-iron clusters in either synthetic or natural systems have not been isolated. In mixed-valence clusters, electron delocalization and antiferromagnetic pairing... 

With strong metal-metal interactions across a bridging ligand, the valence redox orbitals are delocalized molecular orbitals both metal and ligand in character. In mixed-valence compounds, different, discrete oxidation states do not exist since the site of oxidation is delocalized. Strongly coupled systems are like metal-metal bonds in that their electronic and chemical properties are significantly modified from those of related monomeric complexes. As with metal-metal bonds, such compounds can have an extensive multiple oxidation state chemistry based on delocalized molecular orbitals. 

An excellent review of solid-state electron transfer sets out the relationships between many types of processes outside the scope of this review, but it includes some material on solution electron transfer, and an up-to-date summary of work on mixed-valence molecular systems. Although it is well understood that dynamic delocalization of the electrons in a Class II mixed-valence molecule is the same processes as electron transfer between oxidant and reductant in solution, actual measurements of this rate in mixed-valence molecules are still few in number. An advantage of such systems is that in principle, and provided that complications such as phase transitions do not intervene, the rates can be explored over a... 

In mixed valence species, especially symmetric species such as the dinuclear ruthenium Creutz-Taube (CT) ion, questions arise as to whether the valence states are localized, in the CT ion Ru Ru , or delocalized, formally, Ru Ru. The former can become the latter if an electron exchanges rapidly between the two ruthenium centers. Thus, a snapshot taken faster than... 

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