Resolution ligand field states

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... 

The first coordination sphere of acido-pentamine [Cr(NH3)5X]2+ complexes has C4v symmetry and this leads to a tetragonal resolution of the 2Eg state into 2At and 1Bl components. The classical ligand field model predicts that these components will be virtually degenerate. This is based on a combination of pseudo-spherical and quasi-spin selection rules of the shell and will be discussed later on in Sect. 5.2. At present we welcome this example of a pseudo-degeneracy as another opportunity to observe fine details of the interelectronic repulsion interaction which have the proper anisotropy to induce a splitting of the 2Eg term. 

Diamine complexes. The pK values determined for a range of cobalt(iii)-amine chelates indicated enhanced acidity for the protic chelate complexes compared with those with related unidentate ligands." Complete resolution of rac-[Co(en)3] cations has been achieved by paper electrophoresis in a background of d-tartrate and AlC. The crystal structure of (-H)D-[Co(en)3](N03)3 has been determined. The very low quantum yields for the photoreactions of [Co(en)3] have been explained as due to the lack of ligand field excitation for this ion. However, convincing evidence is presented for the reaction of [Co(en)3] " and [Fe(CN)g] under photochemical conditions indicating that this is an efficient photochemical reaction of the cobalt-amine complex in a ligand field excited state (quantum yield ca. 0.2). ... 

Schall et al. (1983) have studied LaF using resolved fluorescence laser spectroscopy. Tunable dye lasers were used to excite known systems of LaF. However, the resolved fluorescence spectra subsequent to excitation of B H-X X" and C Il-X X" bands also showed transitions to X X and a states. They found yet another 12=2 state which was tentatively assigned to Aj. These high-resolution spectral bands facilitated accurate determination of the spectroscopic constants of these states. Schall et al. (1983) also used the ligand-field theory to rationalize their assignments. 

Boltzmann constant R = relative energy resolution T = temperature = natural line width A = ligand field splitting energy d = isomer shift A<5 = inaccuracy of the d determination jy, = relative area (%) under the spectrum Arj = inaccuracy of the t] determination 6 = grazing angle t = lifetime of nuclear excited state p(0) = electron density. 

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