Ligand field excited states

There are two basic approximate approaches to the bonding in molecules—the valence bond (VB) and molecular orbital (MO) theories. Both are applicable to a study of ground states, though in their more usual approximate forms tend to answer different problems. Only the MO theory is useful for a study of excited states. Ligand-field theory is a simpler application of MO theory to systems consisting of a central atom with a partly filled shell surrounded by closed-shell atoms, ions, or dipoles. 

Color from Transition-Metal Compounds and Impurities. The energy levels of the excited states of the unpaked electrons of transition-metal ions in crystals are controlled by the field of the surrounding cations or cationic groups. Erom a purely ionic point of view, this is explained by the electrostatic interactions of crystal field theory ligand field theory is a more advanced approach also incorporating molecular orbital concepts. 

Chromium, hexacyano-, 3, 703, 777 hexaamminecobaltate coordination isomerism, 1, 183 ligand field photochemistry, 1, 398 photochemistry excited states, 1, 398 production, 3, 704 Chromium, hexafluoro-, 3, 927 Chromium, hexabalo-, 3, 889 Chromium, hexaiodo-, 3, 766 Chromium, hexakis(dimethyl sulfoxide)-photoanation, 1, 399 Chromium, u-oxalatodi-reduction... 

We conclude with a consideration of a few other cobalt self-exchange reactions. The reaction in Eq. (9.33) is faster than that involving the ammine complexes (Eq. 9.30) because the water is a weaker-field ligand than ammonia. Thus, the activation energy for the formation of the electronically excited states is lower, as is the change in Co-ligand distances in the two oxidation states. 

The ligand field of a quasi-octahedral coordination sphere acting on the (i-orbitals lifts the degeneracy of the excited spin quartet (and others) as sketched in tier (3). The nature of the resulting states and their energy depends on the strength... 

Calculation of the Slater-Condon, spin-orbit coupling and ligand field parameters. The luminescence of CsMgBr3 Eu2+ is crucially dependent on the local coordination geometry of the Eu2+ dopant. Besides, a geometry change occurs in the excited state 4f 5d1 (see Table 2), leading to shifts... 

Direct probe of ligand field and charge transfer excited states Greater sensitivity than ABS in observing weak transitions and greater resolution due to differences in circular polarization complimentary selection rules aiding in assignment of electronic transitions... 

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