The isotropic proton

Studies on a rechargeable battery material, bismuth doped manganese oxide, were discussed in terms of two unresolved contributions, about 540 cm and 815 cm [64]. (They show no evidence for the isotropic-protons of 9.4.1.) The intensity of the former band decreased whilst the latter increased as more protons were pushed into the lattice. These observations were related to specific water species in the material [64]. INS studies of the electro-active material, NiO(OH), are known [65,66]. 

Although not specifically related to H-bonding these imusual species do involve materials similar to others discussed in this section. There are two of particular interest the isotropic-proton [22] and the free-proton [67]. Both species have been detected in several electrically important materials and so may prove to be of some general interest. 

Isotropic, or nearly so hydrogen potentials in lattices are normally found only for hydrogen-in-metal systems ( 6.6), and materials like 

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In a study of the isotropic proton hyperfine interaction constants for various Fe(R2Dtc)3 complexes and their redox behavior, a simple relationship... 

Delocalization (Z>) and polarization (P) contributions to the isotropic -proton hyperfine coupling constant for the ethyl radical... 

Detection and measurement of the two isomeric forms in solution again is most convenient by proton NMR spectroscopy, in which the isotropic proton hyperfine contact shifts in the paramagnetic tetrahedral isomers make recognition easy, and the amount of the shift reflects the proportion of paramagnetic species in solution (107,110-116, 119). Other methods, including UV/vis spectroscopy (106, 112, 114, 116, 118, 119), magnetic moment determination (105, 106, 109, 110, 115,116,118,119), dipole moment measurement (106,109,114), and IR spectroscopy (118), have also been employed. 

Figure 2 exemplifies the variation of the "isotropic" proton shifts of the Yb3+-alkynyl complex with the temperature. It is noteworthy that the shift of the 01-CH2 protons of the tert-butyl... 

Kashiwagi et al.10) determined the second moment anisotropy for the one-way drawn polyethylene terephthalate sheets discussed above. The three lattice sums S00, S2q and S4o were calculated from the crystal structure determination of Daubeny et al., the proton positions being calculated on the basis of known bond angles and lengths. The isotropic lattice sum S00 was adjusted to a value consistent with the measured isotropic second moment of 10.3G2. The values for P200, P220 etc. were then used to predict the optical anisotropy. The predicted refractive indices for the sheets of draw ratio 2 1 and 2.5 1 are shown in Fig. 10, together with the experimental... 

Numerical results for the shielding field of the benzene molecule are collected in Table 1 for the center of the molecule (labelled COM), and for points along a quarter circle of radius 2.47 A from the -ajcis to the x-axis, see Figure 3 for specification of axes. The radius of the circle corresponds to the distance from the ring center to a proton but, as defined, the points lie in the entirely nucleus-free xz-plane. Except for COM, the entries in the table are labelled by the angle between the z-axes and the direction to the field point. The table includes the isotropic part of the shielding, and the principal... 

Using different DFT functionals and basis sets (Focsan et al. 2008, Lawrence et al. 2008) it was confirmed that the isotropic ()-methyl proton hyperfine couplings do not exceed 9MHz for the carotenoid radical cation, Car-. DFT calculations of neutral carotenoid radicals, Car formed by proton loss (indicated by ) from the radical cation, predicted isotropic P-methyl proton couplings up to 16 MHz, a fact that explained the large isotropic couplings observed by ENDOR measurements for methyl protons in UV irradiated carotenoids supported on silica gel, Nafion films, silica-alumina matrices, or incorporated in molecular sieves (Piekara-Sady et al. 1991, 1995, Wu et al. 

The 13C NMR sensitivity can sometimes be a problem, but for the kind of samples studied here the effective concentration of monomer units is several molar which does not place excessive demands on present Fourier transform NMR spectrometers. In addition to the sensitivity of the chemical shift to structure (9), the relaxation of protonated carbons is dominated by dipole-dipole interaction with the attached proton (9). The dependence of the relaxation parameters T, or spin-lattice, and Tor spin-spin, on isotropic motional correlation time for a C-H unit is shown schematically in Figure 1. The T1 can be determined by standard pulse techniques (9), while the linewidth at half-height is often related to the T2. Another parameter which is related to the correlation time is the nuclear Overhauser enhancement factor, q. The value of this factor for 13C coupled to protons, varies from about 2 at short correlation times to 0.1 at long correlation... 

FIGURE 10.2 The spectrum of the DMPO 011 adduct. The rapidly tumbling adduct affords an isotropic spectrum split by 14N (I = 1) in three lines, each of which is split by the P proton (I = 1/2) in two lines. Overlap of lines, due to AN AH, gives a 1 2 2 1 intensity pattern. 

Fig. 3 Solid state 31P NMR spectra of fosinopril sodium acquired under single pulse, high-power proton decoupling and various conditions of magic-angle spinning (A) static, (B) 2.5 kHz, (C) 4.0 kHz, (D) 5.0 kHz, and (E) 6.0 kHz. The isotropic chemical shift is designated by an asterisk. (From Ref. 15.)...

Assignment of the isotropically shifted signals observed for the CuNiSOD example discussed in the previous paragraph has been achieved by means of anion titrations (not discussed here) and nuclear Overhauser enhancement spectroscopy (NOESY), to be discussed next. In Figure 3.24B the CuNiSOD active site is depicted with histidine nitrogens and protons identified for the discussion of the NOESY results. The copper(II) ion is coordinated to the N ligand atoms of his46... 

The resulting data are shown in Fig. 1.4, in which is plotted the isotropic NMR chemical shift of all 128 protons, obtained from the QM/MM and the isolated cluster calculations as a function of the fully periodical quantum mechanical results. 

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