Skeletal IR spectra

The skeletal IR spectra indeed show a well-defined maximum at 430-420 cm that can be confidently assigned to vto (the only IR-active transverse optical mode) of the Ni-Mg oxide rock salt-t3q)e solid solution. The absence of bands in the far infrared (i.e. below 400 cm ) points to the absence of a spinel phase. However, the additional features, found in the region 900-600 cm , are typically associated with M-0 vibrations of tetrahedrally coordinated cations. Indeed, two absorptions are found in the spectra, near 800 cm and 650 cm . In the case of the Mg-free Ni-Al compound, a similar band was observed at 850 cm This suggests that the band at 800-850 cm is associated with M-0 stretchings of tetrahedrally coordinated... 

Another example concerns C03 O4/AI2 O3 systems also used in the total oxidation of organics as well as precursors of supported Co metal catalysts. In Fig. 18.2 the skeletal IR spectra of the support Siralox 5 (alumina containing 5% Si02, from Sasol) and of two C03O4/AI2O3 catalysts are compared. 

Detailed measurements have been made of the low-frequency Raman spectra of [Zn(py)2X2] (X = C1 or Br) and of the far-IR spectra of the complex where X = Q at liquid nitrogen temperature. It is found that skeletal molecular vibrations couple with lattice vibrations in the crystal, except for the Zn—X stretching vibrations. Force constant calculations indicate the Zn—N bond to be stronger in the bromide, while the Zn—Cl bond is stronger than the Zn—Br bond.477... 

The IR spectra of a number of five-membered N and N,S-heterocyclic compounds have been compared (64CJC43), and the regions of absorption are very similar for the thiadiazole isomers. Characteristic vibrations for 1,2,3-thiadiazoles are 1560-1475, 1350-1280 cm-1 (ring skeletal) 1265-1200, 1190-1175, 1150-950 cm-1 (ring breathing and CH in-plane deformations) and 910-890, 705-670 cm-1 (CH out-of-plane deformations). 

The GC data confirmed the TLC results. TLC detected abietic acid in sample 7 but not in samples 1, 10, and 12. This result indicates that a resin acid concentration of 1% is below the limit of detectability by TLC. TLC revealed dehydroabietic acid in all four samples, and this result was confirmed by GC. The GC data also corroborated the utility of IR spectroscopy. IR spectra showed the isopropyl structure in all four samples, including those for which the acid fraction was less than 10% (samples 10 and 12). Clearly, these isopropyl bands are not from the small amount of residual acid but are caused by skeletal absorptions of the isopropyl group in decarboxylated neutral decomposition products. 

IR spectra of PM and PMC are given in Figure 3 A is from PM, B is from PMC. The peaks in spectrum B are sharper than that of spectrum A because PMC is purer and crystalline. The two split sharp peaks at 3430 cm" and 3344 cm are from asymmetrical and symmetrical N-H stretching, respectively. The sharp peaks at 1630 and 1474 cm" are due to skeletal vibration of C=C and C-N stretching. The C-H bend of CHg and CH3 show as a shoulder at 1451 cm" which overlaps with the peak at 1474 cm. All are consistent with the expected structure. 

IR spectra clearly distinguish the three zirconia polymorphs [57]. The high-temperature cubic phase has only one IR active skeletal mode, found near 550 cm for powders, while tetragonal zirconia (the medium-temperature polymorph) has... 

After evacuation at room temperature a fraction of the thiophene remained adsorbed on the samples. During TPD, desorption of thiophene only was detected from the Y zeolites, while from ZSM5 and MOR desorption of benzothiophene was also observed. This indicates that condensation and cyclization reactions occur on the surface of ZSM5 and MOR. With MOR about half of the adsorbed thiophene was cracked to coke, hydrogen, water, and HgS. In the IR spectra of the spent mordenites (Figure 3) bands at 1584 and 1412 cm", ascribed to skeletal vibrations of the thiophene ring [9], indicated the presence of residual thiophene on the surface after TPD. 

Skeletal mode assignments were proposed from the IR spectra of [(Mesln-Cl)4(InCl)2-(AstBu)4], where Mes = mesityl, and related species, include vlnAs 310 cm-1, vlnCl(br) + vlnAs 210 cm-1, vlnCl(t) 536 cm-1 and vAsC 608... 

Characteristic differences in skeletal mode wavenumbers in IR spectra were seen for high- and low-spin forms of [Fe(pybzim)3](C104)3.H20, where pybzim = 2-(2 -pyridyl)benzimidazole.287 The resonance Raman spectra of cross-trans-linked iron(II) basket-handle porphyrins gave vsFe-Him2 200 209 cm, vsFe py2 182-205 cm-1 (assignments were helped by deuteriation experiments).288... 

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