Infrared band spectroscopy 07 ions

In situ Fourier transform infrared and in situ infrared reflection spectroscopies have been used to study the electrical double layer structure and adsorption of various species at low-index single-crystal faces of Au, Pt, and other electrodes.206"210 It has been shown that if the ions in the solution have vibrational bands, it is possible to relate their excess density to the experimentally observed surface. 

Surface modification of LDPE film can also be brought about by chemical treatment [118] with an aqueous solution of ammoniacal ammonium persulphate in the presence of Ni+2 ions under variable reaction conditions. The investigation of treated surface showed the presence of polar groups (viz. carbonyl and hydroxyl) in the infrared (IR) spectroscopy, with characteristic bands at 1700, 1622 and 3450 cm-1. It is known that the persulphate ion attacks the double-bond-producing epoxy or diol group. However, the destructive oxidation of saturated hydrocarbons does not occur with persulphate alone, but requires the presence of the nickel (II) ion. The authors have proposed the following mechanism of chemical treatment ... 

From the infrared spectroscopy of adsorbed CO it appears that aging treatments, as low as 923 K, lead to a migration of the active isolated copper ions to inaccessible sites. In these conditions an agglomeration is not detected but, after aging at 1173 K, an agglomeration is evidenced both by XRD and by the infrared bands of CO adsorbed on partially reduced bulk CuO oxide. These accessible copper oxide crystallites are probably located at the external surface of the zeolite and are inactive. In fact, the activity remains correlated to the number of Cu VCu isolated ions deduced from the infrared spectra of adsorbed CO and located in the zeolite structure. This correlation holds whatever the treatment and whatever the Si/Al ratio (Table 4). 

For instance, in situ Fourier transform infrared (FTIR) spectroscopy has been used by Faguy and coworkers [79] to study the potential dependent changes in anion structure and composition at the surface of Pt(l 11) electrodes in H S O4 -containing solutions. From the infrared (IR) differential normalized relative reflectance data, the maximum rate of intensity changes for three IR bands can be obtained. Two modes associated with the adsorbed anion and one mode assigned to species is not adequately described as either sulfate or bisulfate the data are more consistent with an adsorbed H3O+—S04 ion pair, possibly with the three unproto-nated sulfate oxygens interacting with Pt sites. 

The application of infrared spectroscopy to the solution of such solvation problems is hampered to a certain extent by the fact that complex formation leads to the appearance of new, skeletal vibrations, the coupling of which with the vibrations of the original molecules makes the vibrational spectrum more complicated. The situation may similarly be complicated by other effects, such as changes in the orbital hybridization, back-coordination, etc. In the coordination of the solvent acetonitrile to metal ions, for example, if only the effect of coordination causing a decrease in the electron density on the nitrogen is taken into consideration, the frequency of the C—vibration would be expected to decrease. In fact, in the course of this process the coordination increases the a character of the C—bond, which is accompanied by an increase in the frequency of the C—vibration [Be 61]. In many cases, it is difficult to assign the infrared bands to the corresponding vibrations the conclusions drawn from the spectral data may therefore be uncertain. 

Gudeman CS, Begemann MH, Pfaff J, Saykally RJ (1983) Velocity-modulated infrared laser spectroscopy of molecular ions the vi band of HCOL Phys Rev Lett 50 727-731... 

Much earlier information on the structure of diazonium ions than that derived from X-ray analyses (but still useful today) was obtained by infrared spectroscopy. The pioneers in the application of this technique to diazonium and diazo compounds were Le Fevre and his school, who provided the first IR evidence for the triple bonds by identifying the characteristic stretching vibration band at 2260 cm-1 (Aroney et al., 1955 see also Whetsel et al., 1956). Its frequency lies between the Raman frequency of dinitrogen (2330 cm-1, Schrotter, 1970) and the stretching vibration frequency of the C = N group in benzonitrile (2255 cm-1, Aroney et al., 1955). In substituted benzenediazonium salts the frequency of the NN stretching vibration follows Hammett op relationships. Electron donor substituents reduce the frequency, whereas acceptor substituents increase it. The 4-dimethylamino group, for example, shifts it by 103 cm-1 to 2177 cm-1 (Nuttall et al., 1961). This result supports the hypothesis that... 

Crisp et al. (1978) were able to follow the course of the cement-forming reaction using infrared spectroscopy and to confirm previous observations. They found that the technique could be used to distinguish between crystalline and amorphous phases of the cement. Hopeite shows a number of bands between 1105 and 1000 cm this multiplicity has been explained by postulating a distortion of the tetrahedral orthophosphate anion. (Two-thirds of the zinc ions are tetrahedrally coordinated to four phosphate ions, and the remainder are octahedrally coordinated to two phosphate and four water ligands.)... 

---