Spectroscopic reduction process

Table 3 Formal electrode potentials (V vs. SCE) for the first reduction process of complexes [ Fe3( CO )8( RC2R) 2] and relative IR and NMR spectroscopic parameters...

The bimetallic complex [Re(CO)3Cl]jtbpq synthesized in this work showed the typical spectroscopic and electrochemical behavior based on analogous polypyridyl complexes of rhenium(l). Re(l) dn tpbq n charge transfer transition and ligand-field n- n transitions are observed. Typical redox behavior of this system consists of Re /Re oxidation and tpbq/tpbq reduction. Such electrochemical activity, particularly in the reductive region, is found ideal for catalytic processes such as CO reduction. IR-SEC studies have shown that the reduction process occurring at -0.50... 

Aurbach and co-workers performed a series of ex situ as well as in situ spectroscopic analyses on the surface of the working electrode upon which the cyclic voltammetry of electrolytes was carried out. On the basis of the functionalities detected in FT-IR, X-ray microanalysis, and nuclear magnetic resonance (NMR) studies, they were able to investigate the mechanisms involved in the reduction process of carbonate solvents and proposed that, upon reduction, these solvents mainly form lithium alkyl carbonates (RCOsLi), which are sensitive to various contaminants in the electrolyte system. For example, the presence of CO2 or trace moisture would cause the formation of Li2COs. This peculiar reduction product has been observed on all occasions when cyclic carbonates are present, and it seems to be independent of the nature of the working electrodes. A single electron mechanism has been shown for PC reduction in Scheme 1, while those of EC and linear carbonates are shown in Scheme 7. ... 

In the nitrogen and boron analogs depicted in Scheme 3-52, two methyl groups provide a sufficient shielding at the NR2 centers (R = Me), while two mesityl groups are needed for protection of the BR2 centers (R = 2,4,6-trimethyl phenyl). Electrochemical studies of l,4-bis(dimesitylboryl)benzene have shown two well-separated one-electron reduction processes, with the formation of the corresponding anion radicals and dianions, respectively (Fiedler et al. 1996). According to UV/vis/near-IR and ESR spectroscopic data... 

In the case of LiC104, there is some spectroscopic evidence of anion reduction below 1.5 V [39], The stable surface species which may precipitate due to the Cl()4 reduction is, among others, Li20. We have no spectroscopic evidence for precipitation of stable LiC10x (x = 1-3) or for LiCl onto noble metals at potentials above those of Li bulk deposition. In any event, the above salt anion reduction processes do not dominate the overall surface film formation on nonactive electrodes at low potentials in most aprotic solvents. Thus, both anions can be considered as only moderately reactive. The onset potential for the reduction of the anions from the third group is about 2 V (Li/Li+). This is clearly demonstrated in Figures 18 and 19, which show FTIR spectra measured in situ from... 

In their complexes, distinction between the three forms, Q, SQ, and Cat, is not always straightforward because oxidation-reduction processes can be metal-based or ligand-based (11-XXV) but spectroscopic techniques and X-ray crystallography can be helpful for example, the C—O lengths are around 1.23 A for benzoquinones, 1.29 A for semiquinones, and 1.35 A for catecholates.98 In the paramagnetic semiquinone complex the electron is located on the ligand. The relative importance of the quinone versus dihydroxo species will depend on the basicity of the metal and the oxidizing ability of the quinone. 

A few electrochemical studies have been also addressed to the structurally characterized (XRD ) VO(acac)2 ". It undergoes oxidation to [VO(acac)2]+ by a process which seems to be reversible in the short times of cyclic voltammetry, but coupled to chemical complications in the longer times of exhaustive electrolysis. One of its salts has been spectroscopically identified as [VO(acac)2](l5). VO(acac)2 also undergoes irreversible or partially reversible reduction processes, particularly in the presence of uncomplexed acac, which ultimately afford [V(acac)3] . The pertinent electrode potentials are listed in Table 8. 

The proposed mechanism for the O2 reduction cycle of the cytochrome c oxidase enzyme is outlined in Figure 6. 8 A two-step 2-e reduction process converts the inactive oxidized Fe3+-Cu2+ bimetallic site to an active Fe +-Cu+ state. Recent kinetic/spectroscopic studies implicate Cub as the initial binding site for dioxygen, thus affirming (for the first time) that Cu(I)/02 interactions are important in CcO. This evidence comes from flash-photolysis of CuB-CO protein derivatives as well as from observations (stopped-flow kinetics/spectroscopy) regarding the direct reaction of O2 with reduced CcO. The... 

The last years in the period of discovery and the some 30 years following it saw several developments in separation techniques for example, the reduction process was introduced for certain rare earths. The variety of chemical methods developed was then applied on an ever increasing scale, sometimes to many kilograms of starting materials especially large amounts were used in the search for the elusive element 61. As examples of the compounds used in the large-scale separation of the rare earths by fractional crystallization, ammonium nitrates and ferrocyanides may be mentioned. Spectroscopic methods were applied to evaluate the success of the separation. A review of the often very laborious separation procedures has been presented by Prandtl (1938). 

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