Diatomic moieties

Alternatively, one may pump an excited electronic state of the diatomic moiety with subsequent dissociation within the excited state. Representative examples are the rare gas-halogen complexes like... 

This type of covalent-ionic resonance, which involves an electron-pair bond in the covalent structure, is widely known. The discussions of Section 7-3 and 8-1(c) show that for 6-electron 4-centre bonding units, another type of eovalent-ionic resonance is also possible, namely that which generates a Pauling 3-electron bond between the diatomic moieties. If we generalize the diseussion of Section 7-3, for example, we may represent this type of resonanee as (1) (2) and... 

In the next chapter we will see how infrared studies on the inhibition of the A. vinosum [NiFe] hydrogenase by carbon monoxide led to the discovery of intrinsic diatomic non-protein moieties directly associated with the catalytic centres of [NiFe]... 

A diverse assemblage of phytoplankton and macroalgae, including diatoms, coccolithophorids (Palenik and Morel, 1988), charophytes (Ivankina and Novak, 1988), and cyanobacteria (Peschek et al., 1988) reduce extracellular electron acceptors. For example, the coastal diatom, Thalassiosira weissflogii, reduces Cu(II) and Fe(III) complexes via three independent reductants as shown in Fig. 3 (Jones et al., 1987) (1) Reductants released by the cells and free in solution that are quickly consumed and are not regenerated in the absence of cells, (2) cell surface moieties that are also rapidly exhausted and can be inactivated by pretreatment with oxidants, and (3) a cell surface reductase whose activity is light-independent. 

The original mechanism proposed for templated silicification was that proposed for diatoms by Hecky et al. and is still referred to today by workers in the field. It was envisaged that the serine/threonine-enriched protein would form the inner surface of the silicalemma, and as such would present a layer of hydroxyls, facing into the silica deposition vesicle, onto which orthosilicic acid molecules could condense. This initial layer of geometrically constrained orthosilicic acid molecules would promote condensation with other orthosilicic acid molecules. The carbohydrate moiety present in the diatom cell wall was... 

In this chapter some systems containing a homo-bimetallic multiple bond, which have been recently synthesized and studied with quantum chemical methods, are analyzed. The chapter is organized as follows. In Section 9.2 a brief description of the computational tools employed in this analysis is presented. In Section 9.3 the classical case of Re2Clg is reviewed. In Section 9.4 group VI homo-nuclear diatomic molecules, namely Cr2, M02, and Wj are discussed. In Section 9.5 homo-bimetallic compounds containing the Cr2, M02 and W2 moieties are described. In Section 9.6 some recently synthesized Fe2 compounds are reported. Finally in Section 9.7 some perspective and some conclusions are offered. 

The most common diatomic bridging hgands are CN , N2, C2, Oj and 02 - The diatomics are the simplest bridging ligands for which the molecular structure of the bridging moiety becomes an issue in the description of the electron transfer reaction coordinate. For example, bond length changes that accompany electron transfer, such as illustrated in Equation (70), must... 

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