Clathrates spectra

IR Data. The IR spectra (in the 600-3000 cm" region) were taken on neat samples in 0.025-mm NaCl cells in the double beam mode with air as reference. The spectra were run on a Beckman IR-7 instrument with a scan rate of 80 cm Vmin and 25 cm Vin. All half-width data were taken with a scale expansion of 10 cm"Vin. at a scan rate of 20 cm"Vniin. All liquid clathrate spectra were analyzed by direct comparison with the spectrum of benzene taken under identical conditions. 

The spectral subtraction technique can be applied equally successfully in the analysis of both the infrared and Raman spectra of inclusion compounds, revealing guest molecule bands which would otherwise be obscured by the more intense host lattice bands. The spectral addition technique is also shown to be useful in simulating clathrate spectra. 

The IR-spectroscopy data (Fig. 2), which agree with the structural data, are indicative of the presence of 4-methylpyridine of two types in cLathrate compounds bonded (a Ligand) and "free" (a guest), which can most obviously be demonstrated by the [NiBijX2] B clathrate spectrum. 

The assumptions (a) - (d) are believed to give an adequate description of the physical situation in the great majority of clathrates. Assumption (a) implies that the spectrum of the host lattice is not affected by the presence of the solute molecules. Little is known about this, but since the host lattice in general is a com-... 

The Pt6Cl12 0.1C2H5C1- 5.7H20 clathrate is a fine brown powder. This substance has no characteristic melting point. It decomposes on heating in the solid phase starting from 70°C. IR spectrum (400-200 cm-1, polyethylene pellets) cm- 344 s, 337 s, 318 vs, and 204 m. 

Figure 7.43 (top) 129Xe CP-MAS NMR solid-state spectra for a the xenon clathrate of Dianin s compound obtained at 1 atmosphere pressure (bottom) the DQ filtered spectrum showing only the resonance due to the doubly occupied cavity. (Reproduced by permission of The Royal Society of Chemistry). 

Nitrogen clathrate in j3-quinol was studied by Scott28) in spite of many experimental difficulties. Among the findings obtained in this study, we may mention the existence of a seven-line spectrum whose intensity depends upon the preparation, history and age of the sample a slow loss of nitrogen by the sample the fact that the line frequencies are independent of the factors which alter line intensities and that the structure may be due to a partial filling of the (3-quinol lattice holes. 

When isoprene was polymerized for the first time in PHTP clathrates, a 1,4-trans structure was assigned to the polymer on the basis of its IR spectrum (] ). In spite of its high steric... 

A single example of terpolymerization is known. It was performed using a PHTP clathrate containing pentadiene, 2-methylpentadiene and 4-m hylpentadiene ( ). Its actual formation was demonstrated by C NMR the spectrum can in the main be interpreted on the basis of the three known copolymers, but there are four signals that should be assigned to mixed triads. No indication of steric disorder has been observed in spite of the presence of three different guests in the same channel. 

HERBSTEIN asked if the method would work if a benzene molecule, for example, were contained in a clathrate crystal. SNYDER replied that, if the molecule migrates through the clathrate relatively rapidly so that it sees an average magnetic environment, then one might indeed be able to obtain a spectrum with very large dipole interactions and quite a bit of structure. But if it tends to stay put in the clathrate site for 0.001 s or so, one would observe the typical broad-band spectrum characteristic of a solid. 

Finally, the excited-state magnetic moment of Xe has been measured by applying a 78-kG external magnetic field to a xenon clathrate absorber [123]. Computer analysis of the broadened spectrum gave = -f0-68(30) n.m. 

Tris(3-bromoacetylacetonato)chromium(III) is a dark red-brown crystalline material, which dissolves in benzene to form a green solution. The infrared spectrum of this chelate exhibits a characteristic strong singlet at 1540 cm. i, whereas chromium(III) acetylacetonate exhibits two peaks in this region, at 1560 and 1520 cm. b The ultraviolet spectrum of the brominated chromium chelate in chloroform exhibits a Xmax at 358 m/i(e = 13,070). The brominated chelate is reported to form a stable clathrate complex with chloroform (m.p. 240 to 241°). ... 

The NMR spectra of all liquid clathrates have one feature in common the entire spectrum is shifted 0.2-0.5 ppm downfield relative to the pure aromatic substance. However, this is thought to be a bulk... 

Since the IR spectrum of the guest benzene is only slightly perturbed from that of neat benzene, the aromatic molecules must interact only weakly with the cations in the liquid clathrate. 

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