Charge transfer bands, correlation with

Figure 21. Correlation of the Cu2+-0 charge transfer band frequency with the global softness of different zeolites.

The IR bands in a number of nickel complexes of triaryl formazans have been assigned by Arnold and Schiele.415 A similar assignment of the electronic bands has been carried out.414 LCAO-MO calculations correlate well with these assignments417 and have been extended to include both inner ligand transitions as well as charge transfer bands and d—d transitions.418 EPR spectra have been used to study the nature of bonding in copper complexes of heterocyclic-containing formazans.419 Metal formazan complexes have also been studied by electrochemistry.283,398 420-422... 

DR. JOHN BRAUMAN (Stanford University) I have a question about the empirical correlations for quantities like charge transfer band energies versus parameters such as the Kosower Z-value. There is a very large literature of that type and there are many, many good correlations for a variety of parameters. You obtain straight lines with your simple dielectric continuum model. It seems to me, however, that one ought to be able to derive these types of relationships directly from the model. And it doesn t seem to be very helpful to say that these relationships are simply empirical and, therefore, not worth the attention. What you want to do is derive the equations and see whether they, in fact, all reduce to the same terms. 

Mixed donor ligands. Tris(acetylhydrazine)iron(iii) trichloride has been pre-pared. ° The effect of pressure on ferric hydroxamates is to cause reduction to iron(ii), the amount of reduction being correlated with the position of the metal-> ligand charge-transfer band. Fe " complexes of A-hydroxyurea have been isolated. 8-Amino-7-hydroxy-4-methylcoumarin (58) forms the complex [FegLjCl ], in which the Fe " ions are in octahedral environments. A magnetic and Mossbauer study of [FeX(ox)2] and [FeX2(ox)] (X = Cl or... 

Porter has correlated solvent shifts on absorption spectra with the photoreactivity of substituted benzophenones.365 He has noted red shifts for the unreactive substituted ketones upon shifting from cyclohexane to 2-propanol, which effect he ascribes to absorption into an intramolecular charge-transfer band which would be stabilized by solvent polarity. He reasons further that the charge-transfer nature of... 

The appearance of similar absorption bands has also been observed upon the formation of a complex between the reduced form of cytochrome c and the simple inorganic acceptor Fe(III)(CN)6[106]. The tunneling distance evaluated from the intensity of this band amounts to 7—10 A. However, more recent experiments have failed to detect such a band [107]. The situation is more favourable in the system [cytochrome c/P870] of the Chromatium reaction centre, where the intensity of the charge transfer band centred at 200 nm could be correlated with the data obtained in kinetic experiments [108]. 

Fig. 9. Correlation of half peak potentials with energies of two visible charge transfer bands. In order of increasing Ep/2 the compounds are Fephen2(CN)2, Fephen2 (CN)2 BF3, Fephen2(CNBF3)2, Fephen2(CNBCl3)2 and Fephen2(CNBBr3)2.

Treatment of [RuC12 (bipy)2] with L- yields [RuL(bipy)2]+ (92) which shows redox activity at 1/2 = +0.39, — 1.67 and —2.00 V vs. SCE.1070,1071 Complexes (93) have been prepared by reaction of L with [Ru(C03)(bipy)2] or [Ru(bipy)2(EtOH)2]2+ 1223 oxidation of (93) to [RumL(bipy)2]2+ can be achieved chemically or electrochemically, the energy of the L - metal charge transfer band in the Ru111 complexes correlating with the values for the RuII/m redox couple.1223 The complexes [Ru-... 

The stoichiometries of the principal species in solution can be determined from both the (concentration-dependent) potentiometric as well as spectrophotometric data. If there are only two siderophore species in equilibrium, spectrophotometric titration data typically show a shift of the ligand-to-ferric ion charge transfer band to longer wavelength with decreasing pH, and an isosbestic point. Using the Schwarzenbach equation (5)125) the data should fit to a linear correlation of Aobs vs (A0 — Aobs)/[H+]n,... 

It would be attractive to correlate the energies of the charge-transfer bands with the electrical conductivities and the activation energies of conduction. A rather close connection of these properties has been demonstrated for Tl3Fe(CN)6 (77), but no obvious correlation could be... 

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