Optical centers, interaction with

Decene complexes with gold, 12 348 Deformation density, 27 29-33 Degradation reactions, heteronuclear gold cluster compounds, 39 336-337 Dehydration reactions, osmium(II), 37 351 Delocalization, see also Valence delocalization added electron, reduced dimer, 38 447, 449 optical centers, interaction with surroundings, 35 380 Density... 

HS redox couple, 33 91-92 HSe/HSe redox couple, 33 98 HSO," /HSO4 redox couple, 33 96 HSO5/HSO5" redox couple, 33 96 [HTcCpJ, 41 29 Huang-Rhys parameter, 35 325 optical centers, interaction with surroundings, 35 380-381... 

ON(SO,)j /0N(S03)2 - redox couple, 33 106 O—O bond, copper proteins, 39 26 homolytic cleavage, 39 60, 62-63 Opposite-spin correlation, 38 439-440 Optical absorption spectrum cytochrome b, 36 418, 420 holoferritin, 36 418-419 Optical centers, interaction with surroundings, 35 319-322... 

Usually, optical bands of centers (atoms, ions, etc.) in solids are broader than those found in gases or liquids. This is because centers are in general more diluted (isolated) in gases or liquids than in solids, and so they are subjected to less important interactions with their neighborhood. 

Chapter 5 will show in more detail how the spectral width of optical transitions of active centers (particnlarly for transition metal ions) is affected by lattice vibrations. For the purpose of this section, we will just mention that these transitions are associated with the outer electrons of the active center (the 3d valence electrons), which show strong interactions with the phonons of the matrix in which they are embedded. As a result, the optical transitions, and particularly the emission lines, are strongly modulated by lattice vibrations. 

As Louis Pasteur first observed (Box 1-2), enantiomers have nearly identical chemical properties but differ in a characteristic physical property, their interaction with plane-polarized light. In separate solutions, two enantiomers rotate the plane of plane-polarized light in opposite directions, but an equimolar solution of the two enantiomers (a racemic mixture) shows no optical rotation. Compounds without chiral centers do not rotate the plane of plane-polarized light. 

P2% ee and 97% yield. Unsubstituted acetophenone and m- or p-bm-lOacetophenone are hydrogenated in less than 1 % chemical yield and pan moderate (30-74%) optical yield with opposite enantioselection. -These results suggest that even halogen atoms (94), placed at appropri-Jate positions in the substrates, facilitate the reaction and exert stereochemical influence through interaction with Ru center. 

Only limited successful examples of asymmetric hydrogenation of acrylic acids derivatives have included the use of chiral Rh complexes (Scheme 1.17). The diamino phosphine (28) utilizes selective ligation of the amino unit to a Rh center and also exerts electrostatic interaction with a substrate. Its Rh complex catalyzes enantioselective hydrogenation of 2-methylcinnamic acid in 92% optical yield [116], Certain cationic Rh complexes can attain highly enantioselective hydrogenation of trisubstituted acrylic acids [ 1171. 2-(6 -Methoxynaphth-2 -yl)acrylic acid is hydrogenated by an (.S ..S )-BIPNOR- Rh complex in methanol at 4 atm to give (.S)-naproxen with 98% ee but only in 30% yield [26]. 

The use of C02 in chemistry normally requires its interaction with metal centers of catalysts one such example is the Kolbe-Schmitt carboxylation of phenol to produce salicylic acid. The potential of C02 as a raw material in the synthesis of carboxylates, carbonates, or carbamates is rather limited. A future aim is the economically attractive synthesis of carboxylic acids, or optically... 

By S02 insertion into the Fe—C bonds of +5 and -5, known to be stereospecific with respect to the iron center (see Section XI,A), and interaction with an optically pure chiral shift reagent, it could be shown that the enantiomers (+)- and (-)-C5H5Fe(CO)[P(C8H5)3]CH2Cl are optically pure (29, 30). 

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