Electron-transfer spectra

It was not until quite recently that the presence of octahedral lanthanide(III) complexes with CN = 6 has been demonstrated. In 1966 Ryan and Jergensen were able to prepare the anionichexahalide complexes of the lanthanides, [MXe] " in non-aqueous (nitriles) solvents [33, 34). Complexes of the type [(C6H5)3PH]3 [MXe] and [C5H5NH]3 [MXe], where M =Pr, Nd, Sm, Eu, Dy, Er, Yb and X- = Cl, Br were obtained as solids. The electronic (/- -/) transitions in these and in hexaiodide, [Mle] -, complexes are extremely weak, except for the magnetic dipole allowed transitions [35). Both electronic and electron transfer spectra (4f- 5d) indicated the presence of octahedral MX species. 

Contents Formal Oxidation Numbers. Configurations in Atomic Spectroscopy. Characteristics of Transition Group Ions. Internal Transitions in Partly Filled Shells. Inter-Shell Transitions. Electron Transfer Spectra and Collectively Oxidized Ligands. Oxidation States in Metals and Black Semi-Conductors. Closed-Shell Systems, Hydrides and Back-Bonding. Homopolar Bonds and Catenation. Quanticule Oxidation States. Taxological Quantum Chemistry. 

Ray, W.J., Jr. and C.B. Post. 1990. The oxyvanadium constellation in transition-state-analogue complexes of phosphoglucomutase and ribonuclease. Structural deductions from electron-transfer spectra. J. Biochem. 29 2779-2789. 

Thornton et al.164 have taken up the problem of gaseous UC16. They determine the photo-electron spectrum with 21.2 and 40.8 eV photons, finding I = 11.28,11.74,12.07, (12.34), 12.45 and 13.28 eV of six signals (with a shoulder in parenthesis). In agreement with photo-electron spectra of SFg and similar molecules, and with electron transfer spectra of d-group hexahalides, the lowest I-value is ascribed to ( r)tlg and the next-lowest to (ji + o)tlu. The shift from the lowest I = 14.1 eV in UF6150) is unusually modest for a chloride (normally, the shift is about 4 eV). These authors also performed a discrete... 

Hence, there are convincing reasons to expect strong chemical effects on the 5f2 system Pu(VI) known from PuOj2 and PuF6. Unfortunately, the electron transfer bands are lower (though broader) in the visible than the 5 f2 internal transitions. Two candidates for the lowest wave-number of such an electron transfer band in PuO 2 253 are situated at 17000 or 19200 cm"1. The spectroscopic difference that MOj does not seem to have electron transfer spectra in the visible is accompanied by a maximum chemical stability of NpOj. However, the rate of lsO exchange at 23 °C in 1M perchloric acid is 0.31 s"1 in NpOj (PuOj is much slower, UOj much more rapid) but below 6 10"7 s"1 in NpOj2231. Much of the reported chemistry of transuranium elements is influenced by redox reactions, due to products of the intense radioactivity. Thus, lg of the uranium... 

Fig. 3. The relative position of molecular orbital energies in regular octahedral MX, and tetrahedral MX, complexes. The arrangement is known from the M.O. interpretation of electron transfer spectra. The relative distances to the two highest empty sets of orbitals is underestimated, it may be much larger.

In all of these excitation processes, one meets the same problem as in electron transfer spectra (4, 105) that the difference of ionization energy of the stronger bound orbital b and the less strongly bound a is corrected by the interelectronic repulsion A%(a, a) in the a orbital and by the charge-separation effect (4) represented by the hole-electron attraction A (a, b) ... 

Christian Khxbiill Jorgensen Optical electronegativities from electron transfer spectra... 

One problem which is of great interest and which has not been tackled directly because of the great instability of the obvious substrate is the electron affinity of the hydroxyl radical. Lattice energy calculations, and thermodynamic cycles, can be made consistent with any value between 40 and 70 kcal., as can the electron transfer spectra. Some years ago the author interpreted a number of microwave studies of flames as indicating an electron affinity of hydroxyl of 62... 

The most controversial and one of the most important quantities is the bond dissociation energy for the reaction HO2 H + O2. The understanding of autoxidation depends to some extent on this value. Much higher values have been postulated—e.g., 67 kcal. by Walsh (26). The evidence for the lower value of 36 kcal. is, apart from the agreement with kinetic data, based on the peaks of the electron transfer spectra of various ferric ion pair complexes. These allow an estimate of the electron affinity of the HO2 radical in solution and consequently produce a value of 102 kcal. for Dh.. .02H and 36 kcal. for Dh.. .02- This in turn leads to a dissociation constant of 10 for the HO2 radical in aqueous solutions. 

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