Far IR spectra

Saturated five-membered heterocyclic compounds are non-planar, existing in half-chair or envelope conformations. The far-IR spectra of THE and 1,3-dioxolane (127) show both to have barriers of ca. 0.42 kJ moP ... 

Distinguishing between the fac- and mer-isomers is theoretically possible with far-IR spectra, as the mer-isomer (C2v symmetry in the coordination sphere) should give rise to three u(Os—X) stretching bands, while the C3v... 

Figure 3.102 Far-IR spectra of (a) traris-Pt(PEt3 )2C14 (b) rram-Pt(PEt3)2Br4 (c) trans-Pt(PEt3)2l4 (d) cis-Pt(PEt3)2Cl4 (e) cis-Pt(PEt3)2Br4. Platinum-halogen vibrations are shaded.

The Raman, mid- and far-IR spectra of liquid and solid CH3GeD2NCO and CD3GeH2NCO were assigned and applied for the conformational analysis of these isocyanates553. 

If one is interested in spectroscopy involving only the ground Born Oppenheimer surface of the liquid (which would correspond to IR and far-IR spectra), the simplest approximation involves replacing the quantum TCF by its classical counterpart. Thus pp becomes a classical variable, the trace becomes a phase-space integral, and the density operator becomes the phase-space distribution function. For light frequency co with ho > kT, this classical approximation will lead to substantial errors, and so it is important to multiply the result by a quantum correction factor the usual choice for this application is the harmonic quantum correction factor [79 84]. Thus we have... 

ASTM-Wyandotte Index, Molecular Formula List of Compounds, Names and References to Published Infrared Spectra. Philadelphia, PA ASTM Special Technical Publications 131 (1962) and 131-A (1963). Lists about 57,000 compounds. Covers IR, near-IR, and far-IR spectra. 

Analysis of the far IR-spectra of 3,4-dihydro-2//- pyran (13) (72JCP(57)2572> and 5,6-dihydro-2/f- pyran (14) (81JST(71)97> indicates that for both molecules the most stable conformation is a half-chair form. The barrier to planarity is greater for the former compound. These preferred structures are in accord with the half-chair conformation established for cyclohexene and its derivatives. The conformational mobility of cyclohexene is greater than that of the 3,4-dihydropyran. The increased stabilization of the pyran has been attributed to delocalization of the v- electrons of the alkenic carbon atoms and the oxygen lone-pairs (69TL4713). 

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... 

A study of the far IR spectra of the liquid, glass and crystalline states of ZnCl2 has been reported960 with particular reference to the effects of order and temperature on band shape. 

The far IR spectra of the [Znd4]2- anion in salts with the 1,10-phenanthrolinium and 2,2-bipyridinium cations have been reported.1039 The anion in the former salt appears to be tetrahedral, while that in the latter is believed to be halogen-bridged. 

It is particularly important to be able to distinguish between cis and trans isomers. In solution, NMR spectroscopy (2H, 31P, 13C) is the most useful technique in the solid state the far-IR spectra are usually diagnostic, since both the number of bands (two for cis, one for trans) and the frequency of absorption (vPd x) are characteristic of the isomer present. 

When the M4CI QD s exist at defect concentration levels in a QS of M4I QD s and vice-versa, the optical reflectance and mid,far-IR spectra appear to be dominated by the spectral diagnostics of the QS. On the other hand, when the... 

Figure 4. In situ FT-FAR-IR spectra of NIKNaZ (lower) and HNaZ (upper) for (A) zeolite A (B-B) faujasite, Si/Al=1.25, 2.5, 3.8. (F represents a framework mode, A is a supercage NH + cation mode and S are residual sodium cation modes).

Figure 5. In situ FT-FAR-IR spectra of Co2+ ion-exchanged NaseY containing 6, 14 and 17 Co2 + cations per unit cell. (S represents a residual Na+ site II cation mode, I, III" and I designate the respective Co2+ cation site modes. Higher loading studies show that site II Co2+ lies in the same region as site II Na+).

Figure 7. In situ FT-FAR-IR spectra of (A) vacuum thermally deamminated/dehydrated Na i Y showing residual sodium sites, and (B-C) the outcome of exposure to Co2(C0)8 vapour for 5 and 15 minutes respectively, showing the formation of accessible Co2+ site II and III cations (see text).

Grace) and Paul Kasai (IBM), as well as helpful technical discussions. The assistance of Ms. Caroline Gil in obtaining the far-IR spectra, and Mr. Ted Huber in the synthesis of some of the materials is also greatly appreciated. 

IR spectroscopy can be used to characterise the formation of ionomers by studying the environment of the anions [85, 86]. Risen and co-workers [87, 88] used far-IR spectra (150 to 400 cm"1) to demonstrate the sensitivity of low frequency vibrations to the anions and cations and the degree of cluster formation in ionomers. For example, styrene sulfonic acid ionomers with Na+ cation shows absorption bands at 220 cm 1, whereas the Cs+ cation shows bands at 100 cm 1. 

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