Shift paramagnetic

Hinckley, C. C. Paramagnetic shifts in solutions of cholesterol and the dipyridine adduct of trisdipivalomethan atoeuropium(III). A shift reagent. J. 

Figure 3. Monitoring the uptake of Li+ into human erythrocytes after incubation in media containing 2 mM Li+ using 7Li NMR spectroscopy. The signals corresponding to the intra-, and extracellular Li+ are separated by the presence of the paramagnetic shift reagent, Dy(P30io)2, the extracellular medium [34].

Nitronates, in which the /V -oxide fragment is absent, are characterized by strong paramagnetic shifts of the signals of the a-C atom and the proton bound to this atom (see, e.g., entry 5 in Table 3.10 and entries 2 and 9 in Table 3.11). 

It should be noted that the signals of the -CH=N fragment in all cations (349) are characterized by strong paramagnetic shifts compared to the analogous resonances of the starting nitronates (348) (the signal for the proton is shifted... 

In the cyclic 1 1 complex, glucose is held close to the anthracene aromatic face, as represented in Scheme B10.4.1. In fact, the 1 H-NMR spectrum exhibits a very large paramagnetic shift for the H3 proton (—0.3 ppm), which thus points towards the re-electrons of the anthracene moietya,b). 

In the normal average (AE) approximation AE is equated with the lowest energy (highest wavelength, Xmax) transition in the UV region. If AE is small, the effect is large and a shift to low field results. This is frequently referred to as a paramagnetic shift (even... 

NMR has also been used to characterize binding [22, 23]. When cyt c binds to ccp the paramagnetically shifted heme methyl groups of cyt c shift further downfield by 1-2 ppm. Normally, binding occurs in the fast exchange regime, so that the fraction bound can be assessed from the frequency shift (Fig. 10). Two... 

Magnetic susceptibilities of solutions — These are useful parameters for determining equilibrium constants for reactions involving spin changes. The Evans nmr method utilizes the observed shift in the resonance line (say of a proton of t-BuOH or hexamethyldisilox-ane) in solution when a paramagnetic substance is added. The paramagnetic shift A/ is related to the magnetic moment (jj, of the solution at TK by the approximate expression... 

Lanthanide Shift Reagents.—New theoretical treatments of the origin of the paramagnetic shifts induced in the n.m.r. spectra of substrates bound to... 

Bu ) have been used to induce paramagnetic shifts in C n.m.r. spectra. Thus, all sets of shifts in 2,2-dimethylpropan-l-ol varied with concentration of the added shift reagent, except when using the Gd complex where no shift was experienced. In the study of Bu"NH2, Pr"NH2, and n-CjHjjNH2, and upheld shift of the C-2 resonance was observed, but a comparable downfield shift occurred with Bu"OH. Induced shifts of C resonances were utilized in the analyses of the spectra of piperines" and ribose-5-phosphate. ... 

A chiral dichlororuthenium(IV) complex of a Z)4-symmetric porphyrin, [Ru (Z)4-por )(Cl)2], has been prepared by heating [Ru (Z>4-por )(CO)(MeOH)] in CCI4. The complex is characterized by NMR (paramagnetically shifted pyrrolic protons at = 52.3 ppm), FAB-MS, and magnetic susceptibility measurement (/.teff= 3.1/.tB). It is a very active catalyst for enantioselective alkene epoxidations using 2,6-dichloropyridine A-oxide as the terminal oxidant, with a turnover number of up to 2000 the ee of the epoxides is 50-80%. The complex can be incorporated into sol-gel and turnovers of over 10" can be achieved." ... 

For phosphorus involving tetra-, penta- or hexa- coordination the importance of d electrons (even if quantitatively small) must not be underestimated <1968,5) it is especially easy to detect as it strongly decreases the paramagnetic shift from which a net high-field shift arises. To consider these -contributions on a theoretical basis is rather complex<1964,1) and is at present limited to qualitative conclusions/1968,5) The case of the assumed PBr4Q ion, for which a shift of — 150 p.p.m. is observed (compared with —225 for PBr3) is rather interesting in this respect/1969 111... 

By far the most NMR studies have been concerned with the amine adducts of Ni(R-dtp)2 complexes. The green complexes formed with primary (mono-and bidentate) and heterocyclic (mono- und bidentate) amines and the yellow-brown five-co-ordinate adducts with secondly amines exhibit paramagnetic shifts in their NMR spectra. The use of paramagnetic NMR shifts in mapping unpaired electron spin distributions of paramagnetic complexes has been reviewed 378-381) jhe upfield paramagnetic shifts of NH protons are diagnostic... 

For high-spin ferric porphyrin with axial symmetry, the paramagnetic shift, (AH/H) is given by Eq. (2) [3] ... 

Fig. 6a, b. Temperature variation of the paramagnetic shift of ring methyl proton resonances of (a) diaqua hemin, and (b) aqua hydroxo hemin complexes, in 5% aqueous SDS micelles. (Taken from Ref. 20)... 

The effect of the micelles on the paramagnetic shifts of the heme was very clearly demonstrated [22] in NMR of labelled cyanide in [Fe(PP)(Ci"N)2]- and [Fe(PP)(py)(Ci N)] in different micelles as well as in the absence of micelles (Fig. 9). A pronounced systematic downfield shift of the bound cyanide signals is observed on going from a solution without micelles to SDS, to TX-lOO and to CTAB micellar solutions which is also the trend in increasing hydrophobicity. The signal is known to be extremely sensitive... 

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