Solid-state shifts

Figure 11. 15N NMR MAS NMR spectra and tensor results for [15N4]-ring labeled metalloporphyrins. A, 8.45 Tesla 15N MAS NMR spectrum of Fe(tetraphenylporphyrinate)(PhNO)( 1 -methylimidazole), vr = 2.6 kHz. B, graph showing correlation between experimental and DFT computed I5N tensor elements for Fe(TPP)(PhNO)( 1 -Melm) ( ) and Fe(TPP)(CO)(l-MeIm) (O). The mean experimental and theoretical shieldings over the four non-equivalent sites in each molecule are shown since the solid state shifts are not specifically assigned. Slope = 0.847, R2 = 0.995.

Table 3. One and two-photon thresholds (in eV) of trans-polyenes, CnHn+2, in alkane matrices[58] and in the Pariser-Parr-Pople model[21]. The solid-state shift of 0.40eV of the ionic 1 1B state yields gas-phase values up to n = 12 covalent 2M+ shifts of 0.05eV are neglected.

For an absolute agreement between the observed and calculated crystal field effects in such dipolar crystal lattices, the zero point vibrations have to be considered, as Bersohn pointed out. Furthermore, we think that the part of the solid state shift is due to the contribution of the quadrupole polarization (antishielding factor). The inner shell electrons of the atom considered experience an induced quadrupole moment under the influence of the external fields. This... 

Since the two ions are essentially the same chemically but merely differ slightly in how they pack into the crystal, it is not surprising the average shifts do not differ significantly. For comparison, the chemical shift of a 1 M solution of calcium formate is 8 172 ppm. Again, we expect similarity, but not identity, with respect to the isotropic solid-state shift. In the solution case the ion is surrounded by a solvation sphere, whereas in the crystal, the solvent is other ions. It is not unreasonable to expect a moderate shift due to that effect. It is also very often the case that principal values are individually more sensitive to intra-and intermolecular effects than are isotropic shifts. ... 

Tautomerism in the solid state can be studied by or CP-MAS NMR spectroscopy. Crystals (but also those of substantial defects and amorphous samples) contain usually one predominant form but tautomeric exchange can occur also in the solid state especially if the NMR spectra are recorded at not low enough temperatures. In the former case, solid-state tautomerism can be compared with the corresponding solution-state tautomerism. In case of agreements, tautomer assignments (requiring often in addition computed NMR spectra) are most likely, taking the specific solid-state shift effects (see above) into account. 

Fig. 1 shows the block diagram of the vibrometer, in which the most sensible to small phase variations interferometric scheme is employed. It consists of the microwave and the display units. The display unit consists of the power supply 1, controller 2 of the phase modulator 3, microprocessor unit 9 and low-frequency amplifier 10. The microwave unit contains the electromechanical phase modulator 3, a solid-state microwave oscillator 4, an attenuator 5, a bidirectional coupler 6, a horn antenna 7 and a microwave detector 11. The horn antenna is used for transmitting the microwave and receiving the reflected signal, which is mixed with the reference signal in the bidirectional coupler. In the reference channel the electromechanical phase modulator is used to provide automatic calibration of the instrument. To adjust the antenna beam to the object under test, the microwave unit is placed on the platform which can be shifted in vertical and horizontal planes. 

Olivier L, Poupko R, Zimmermann FI and Luz Z 1996 Bond shift tautomerism of bibullvalenyl in solution and in the solid-state—a C-13 NMR-study J. Phys. Chem. 100 17 995-18 003... 

Hydrogen bonding to a carbonyl group causes a shift to lower frequency of 40 to 60 cm k Acids, amides, enolized /3-keto carbonyl systems, and o-hydroxyphenol and o-aminophenyl carbonyl compounds show this effect. All carbonyl compounds tend to give slightly lower values for the carbonyl stretching frequency in the solid state compared with the value for dilute solutions. 

The reaction path shows how Xe and Clj react with electrons initially to form Xe cations. These react with Clj or Cl- to give electronically excited-state molecules XeCl, which emit light to return to ground-state XeCI. The latter are not stable and immediately dissociate to give xenon and chlorine. In such gas lasers, translational motion of the excited-state XeCl gives rise to some Doppler shifting in the laser light, so the emission line is not as sharp as it is in solid-state lasers. 

In the solid state the CH tautomer (78a) is always readily identified, but the OH and NH tautomers (that, in some cases, coexist in the crystal (73CSC469)) are difficult to differentiate due to the strong hydrogen bonds that shift the u(CO) band to the region of pyrazole vibrations. This source of complications is not present in the fixed forms that can always be identified by their IR spectra, both in solution and in the solid state. 

Maintenance on gas trucks is also higher than with electric vehicles. About 5 percent annually of the initial cost applies to internal-combustion equipment, and about 2 percent annually to electric. A special feature on electric trucks with solid-state controls is the use of modules or circuit boards, which can be replaced as units and rebuilt at the factoiy. Typical maintenance costs for trucks operating five 8-h shifts per week are in the order of 3.15 per hour for gas vehicles and 1.78 per hour for electric ones. Under these conditions, energy costs are typically 9.3 cents per hour for gas trucks and 5.1 cents per hour for the electric units. 

Figure 3 Characteristic solid state NMR line shapes, dominated by the chemical shift anisotropy. The spatial distribution of the chemical shift is assumed to be spherically symmetric (a), axially symmetric (b), and completely asymmetric (c). The top trace shows theoretical line shapes, while the bottom trace shows rear spectra influenced by broadening effects due to dipole-dipole couplings.

High-Resolution Solid-State NMR Study of Reversible 1,5-Proton Shifts in Organic Solids [90MRC(S)29] NMR of Pyrazoles ... 

Interpolation methods based on N chemical shifts require the use of the general equations.Those reported in the previous edition (76AHCSl,p. 29, see also 82JOC5132) have been slightly modified for the present purpose. We call / x the observed average property, and the property of the individual tautomers (A or B), / ma and / mb a corresponding property that can be measured (in a model compound or in the solid state) or calculated theoretically, and P and / b the correction factors defined as P = -... 

Generation of reaction networks with RAIN resonance structures and tautomerism Solid-state NMR studies of reversible 1,5-H shifts Tautomeric equilibria (AMI, MNDO, PM3)... 

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