P spectrum

Table 5 shows the most important NMR data of halophosphates. In the species containing fluorine, apart from the chemical shifts of the P-spectra, the F-spectra and the coupling constants Jpp are available for the discussion of bonding. The importance of NMR spectroscopy for purity control, for equilibrium measurement, as kinetical method in the investigation of reaction processes and for the identification of unstable compounds shall not be discussed here, though these apphcations are of great importance for the halophosphates too. 

In the series of the dimethylmetal difluorophosphates from aluminium to thallium, the chemical shift in the P-spectra of [(CH3)2T1(P02F2)]2 is most striking. 

A number of Se(ll) and Te(Il) complexes with dithiocarbamate (and related) ligands apparently form paramagnetic MS2(C2v) chromophores in solution (150). The electronic spectra of these systems can be treated as p-p spectra, and have been successfully interpreted using the AOM. 

Figure 10.1 The absorption (A), fluorescence (F) and phosphorescence (P) spectra of compound A...

In fact, the ti -contributions extend over all the energy range of interest so that even if the -contributions are dominant, there is always some 6 -contribution of the appropriate symmetry and, as a consequence, the levels are going to be visible to some degree in the S2 p spectra. 

Fig. 11. Changes In gated NMR spectra during the cardiac cycle. Top panel isovolumic left ventricular pressure In a ferret heart paced at 0.99 Hz in 8 mM [Ca +]. NMR spectra were acquired at the two times indicated on the pressure record (a) 10 ms prior to stimulation (b) 75 ms after stimulation. Middle panel shows gated F NMR spectra (each from 800 acquisitions) recorded at (a) and (b), as indicated. The bound (B) and free (F) peaks of 5F-BAPTA exhibit distinct chemical shifts at approximately 8 and 2 ppm, respectively, downfield from a standard of 1 mM 6-Ftryptophan at 0 ppm. It appears that the free [Ca +] varied during the cardiac cycle. Bottom panel shows gated P spectra (400 scans) acquired at times a and b in the same heart. The major peaks correspond to phosphocreatine (0 ppm), ATP (the three peaks upfield from phosphocreatine), and inorganic phosphate (the small peak at 4-5 ppm) (Reproduced from Marban et al. Circ. Res. 1988 63 673-678 [311] with permission of Lippincott, Williams Wilkins).

The P spectra were recorded on a Brucker MSL-300 spectrometer operating at 121.4 MHz s. The P NMR spectra were obtained under MAS conditions by use of a double bearing probehead. A single pulse sequence was used in all cases and the delays were chosen allowing the obtention of quantitative spectra (typically the pulse width was 2 ms (10°) and the delay was 10 to 100 s. The number of scans was 10 to 100. Spectra were refered to external H3PO4 (85%). 

Figure 3.29 (a) Outline of the absorption, A fluorescence, F and phosphorescence, P spectra of a rigid polyatomic molecule. X = wavelength, vertical axis = absorbance (A) or emission intensity (F, P). (b) The Stokes shift of the absorption and fluorescence spectra is defined as the difference between their maxima. When this shift is small, there is a substantial spectral overlap between absorption and emission, (c) Jablonski diagram and outline of the absorption and fluorescence spectra of azulene, an exception to Kasha s rule. The energy gap between S0 and Sj is very small, that between Sj and S2 is very large... 

Relative to an external H, P04 standard, f H and 31 P spectra recorded in benzene solution. Relative to internal Si(CH3)4. 

In addition to these phenomena, the 13-membered compound g, also shows a temperature dependent NMR effect in the 3 P spectra. The 31P values shown in the Table were observed at -52°. At higher temperatures the two phosphorus signals broaden and move closer together. This behavior suggests rapid tautomerism of the two isomeric forms of this compound. The high temperature limit where the two signals for 8a and 8b coalesce was not reached in chloro-form-d. ... 

Several polarized absorption spectra have been described for a variety of unheated and heated natural and synthetic orthopyroxenes (e.g., Bancroft and Bums, 1967a Runciman et al., 1973b Goldman and Rossman, 1976, 1977a, 1979 Rossman, 1980, 1988 Zhao et al., 1986 Steffen et al., 1988). In fig. 5.15, representative spectra are illustrated of two orthopyroxenes, enstatite Fs14 5 and ferrosilite Fs864. The a spectra show a very intense band centred near 10,700 cm-1. The P spectra consist of two bands located near 11,100 cm-1 and between 5,400 to 4,900 cm-1, with a shoulder around 8,500 cm-1 becoming well developed in Fe2+-rich orthopyroxenes. The y spectra of Mg2+-rich... 

Since Fe2+ ions are concentrated in the acentric M4 sites of cummingtonite, the intense band around 10,000 cm-1 in the p spectrum (fig. 5.19a) arises from absorption by Fe2+ ions in this very distorted site. The increased intensity and width of absorption bands in the a and y spectra of grunerite and the broadening of the intense band in the P spectra result from increased occupancies of Fe2+ ions in the more regular Ml, M2 and M3 octahedral sites. 

As already mentioned in Section 4, the 5 s and 5 p core level spectra of the 5f-series and a number of the preceding elements should show pronounced effects of giant Coster-Kronig fluctuation and decay processes much in the same way as happens in the 4.S, 4 p spectra in the range 48 Z < 70. In the case of the 5 p spectrum, the gCK interaction process becomes... 

Figure 5. Intensity of monomer (M-) and polymer radical (P-) spectra at increasing VAc concentration and other conditions as given in Figure 2...

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