Nickel absorption spectra

The nickel in urease is nonmagnetic and appears to be in the oxidation state Ni(II). The broad optical absorption spectrum is influenced by ligands to the metal (Fig. 1). The spectrum obtained in the presence of the competitive inhibitor mercaptoethanol, after correction for Rayleigh scattering by the protein (31), shows absorption peaks at 324,380, and 420 nm, with molar absorption coefficients of 1550,890, and 460 A/-1 cm-1, respectively. These were assigned to sulfur-to-nickel charge transfer transitions. The spectrum is changed by addition of other inhibitors, such as acetohydroxamic acid (Fig. IB). Similar... 

Fig. 7. Optical absorption and magnetic circular dichroism spectra of oxidized hydrogenase from M. thermoautotrophicum (AH strain), nickel concentration 120 pM. (a) Optical absorption spectrum, at room temperature the absorption is predominantly due to iron-sulfur clusters, (b) MCD spectra recorded at 1.53, 4.22, and 8.9 K, in a magnetic field of 4.5 T MCD is predominantly due to Ni(III), which is the only paramagnetic species in the oxidized enzyme. Reproduced, with permission, from Ref. 57.

A.S. Wagh and S.Y. Jeong, Chemically bonded phospho-silicate ceramics, U.S. Patent No. 6,518,212, 2003. P. Sivaprasad, K. Ramesh, and Y.P. Reddy, Optical absorption spectrum of nickel doped MgKP04-6H20, Solid State Commun., 73 [3] (1990) 239-241. 

An example of the use of this approach is shown [12] for the nickel-thiocyanate, Dowex-50W-X4, and Dowex 1-X4 system (Fig. 7). In the lowest SCN concentration range, the slope is -1 and NiSCN is identified in the middle SCN concentration range the slope increases from negative to positive and finally with further increase of SCN" concentration it reaches +4 to signal the predominance of the fully coordinated Ni(SCN)g" complex in the anion-exchanger phase. The absorption spectrum of this last complex is shown in Fig. 8. It has not yet been observed in concen-... 

The cobalt(II) corrole anion prepared as above was characterized primarily by electron spin resonance (esr) and absorption spectroscopy. When prepared via sodium film reduction, the cobalt(II) corrole oxidizes rapidly to the corresponding Co(III) corrole on exposure to air. When prepared by the other methods, it is moderately stable in air in the presence of a reducing agent. Attempts to prepare the neutral form of the initial Co(II) corrole anion, by protonation with perchloric acid, resulted in formal oxidation to the Co(III) derivative. Interestingly, further protonation of the Co(III) corrole with perchloric acid led to what appeared to be a protonated Co(III) corrole. Certainly, the absorption spectrum of this species is similar to that of the corresponding neutral nickel(II) corrole complex. However, the exact nature of this protonated material has not been fully elucidated. 

Bis(4-imino-2-pentanonato)nickel(II) crystallizes from a benzene-petroleum ether mixture as dark red needles or as fine red-orange needles. The two forms have identical melting points. The compound is very soluble in chloroform, but less soluble in benzene, pyridine, and carbon tetrachloride, and very insoluble in water. The compound crystallizes from pyridine without adduct formation. The compound is diamagnetic and apparently has the trans configuration. Partial resolution in optically active fractions has been achieved by means of a chromatographic technique. Molecular weight determinations indicate that the compound is monomeric in chloroform and benzene solution. The visible absorption spectrum of this compound in chloroform is characterized by a band centered at 552 m/i (e = 43). The ultraviolet absorption maxima for solutions in 1 1 benzene-petroleum ether occur at 298, 348, and 364 m x (e = 4150, 4760, and 4460, respectively). ... 

Nickel cyanides seem to behave differently from the isomorphous complexes of Pd and Pt. Already in the free state the spectrum indicates the presence of very weak bands due to d—d transitions, giving rise to the orange coloration of concentrated solutions. The passage to the crystalline state results in an absorption spectrum which is not very sensitive to the nature of the cation, except perhaps for BaNi(CN)4, 4 H2O, and is structured in the same way as the spectrum of the free ion except for the relative intensity of the absorption bands. 

Synchroton radiation has been employed as a spectral source for a study of the absorption of HCN and DCN in the wavelength range 80—120nm. A vacuum-u.v. spectrophotometer for absorptions in the region 105—200 nm has been described. Solid-, liquid-, and gas-phase samples could be analysed at temperatures from —200 to 100 °C and at pressures between 0 and 150 atmospheres. The absorption spectrum of tra j-di-imide in the vacuum-u.v. has been measured. First-derivative u.v. spectroscopy has been employed in the analysis of Watts nickel plating solutions for trace amounts of saccharin. Impurity levels of 0.1 p.p.m. have been recorded. A wavelength modulated derivative spectrophotometer with a multi-pass absorption cell has been developed for the automatic analysis of atmospheric pollutants. Traces of SOj, NO, and NO2 were detected with limits of 15, 13, and Sp.p.b., respectively. A double-beam single-detector absorption spectrometer has been constructed. Independence... 

Hydrated salts of hexaaqua ions have been studied for a long time. In Figure 18 the visible and MCD spectra of some nickel(II) complexes are shown. In the case of Ni(H20)6(Br03)2 both B and C terms have been found to contribute to the MCD spectrum, the spectrum at 4.2 K being dominated by the C terms. This study supports the view that the state is interacting via spin-orbit coupling with the giving the characteristic double-peaked 13 000 cm band ( red band ) of the absorption spectrum. 

With atomic species, the near edge structure is of no further interest. With molecular adsorbates, the near edge X-ray absorption is dominated by intramolecular transitions (/X- and (7-resonances). Their dependency on the polarization provides information on the orientation of the molecule. From the energy of the a-resonance intramolecular bond lengths, tab can be estimated for simple molecules. Figure 5.97 shows an X-ray absorption spectrum of NO adsorbed on a nickel surface. 

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