Effective Shift Reagent Research Articles

Исследование молекулярного строения по спектрам ЯМР высокого разрешения, трансформированным парамагнитными комплексами

This paper provides an overview of the features specific to the nuclear magnetic resonance (NMR) of paramagnetic molecules. These features can be attributed to the hyperfine or electronic coupling between unpaired electrons, which are localised on the coordinating ion, and resonant nuclei. That leads both to the paramagnetic broadening and to the paramagnetic shifts (contact and pseudo-contact ones) of resonance lines in the NMR spectra. A contact shift is observed when the probability of an unpaired electron location in the place of a resonant nucleus differs from zero. Therefore, these shifts constitute a source of information on the nature of the metal-ligand bond as well as on the ligand electronic structure. Pseudo-contact shifts characterise the spatial structure of the molecule, thus being important for solving various structural problems. This paper covers pioneering works describing the specifics of the NMR spectra transformed by adding paramagnetic complexes of iron-group elements on the example of cobalt and nickel complexes, as well as complexes of rare-earth elements on the example of europium. We present main features of the paramagnetic additives method, allowing resolution of difficulties associated with large paramagnetic broadening of resonance lines in high-resolution NMR spectra. Of iron-group elements, a paramagnetic ion Co 2+ is shown to be an effective shift reagent. In some cases, a Ni 2+ ion may also be used for this purpose. The paper covers conditions for recording the NMR spectra of samples containing paramagnetic additives; solvents used for this purpose; as well as temperature variations of the studied samples in the context of resonance signal detection.

TmDOTP(5-) as a (23)Na shift reagent for the subcutaneously implanted 9L gliosarcoma in rats.

The use of TmDOTP(5-) as an in vivo (23)Na NMR shift reagent (SR) for subcutaneously implanted 9L gliosarcoma was evaluated. TmDOTP(5-) produced a single sharp extracellular peak after about 50-60 min of infusion, and did not cause any changes in the (31)P resonance areas or chemical shifts, suggesting that the SR is homogeneously distributed in the extracellular space and does not alter tumor bioenergetic status. TmDOTP(5-) and CoEDTA(-) as extracellular space markers gave identical results for relative extracellular space (0.25 +/- 0.03 and 0.25 +/- 0.04, respectively) and intracellular Na(+) concentration (19.3 +/- 4.0 mM and 18.6 +/- 3.9 mM, respectively), indicating that the biodistribution of the SR is the same as the well-accepted extracellular space marker. The in vivo T(1) and T(2) relaxation times of intra- and extracellular Na(+) were also measured. Our results indicate that TmDOTP(5-) promises to be an effective shift reagent and extracellular space marker in the 9L gliosarcoma and perhaps other tumors. Magn Reson Med 45:436-442, 2001.

Measuring Nitrate in Plant Cells byin VivoNMR Using Gd3+as a Shift Reagent

NMR investigations of nitrate in plant cells and tissues have hitherto been limited by the indistinguishability of the signals from intracellular and extracellular nitrate. Gd3+is shown to be an effective shift reagent for14N and15N nitrate NMR signals, resolving the internal and external nitrate signals in plant tissues, including cell suspensions and root material. However, time-course experiments show that, while the use of Gd3+allows nitrate levels to be monitored over extended periods, it also has adverse effects on growth and nitrate uptake. Accordingly, a number of chelated forms of gadolinium were investigated, and it is concluded that the NMR contrast agent Gd(DTPA-BMA) is likely to be a suitable shift reagent for physiologically relevant studies of nitrate transport in roots.

In vivo sodium chemical shift imaging

The shift reagents thulium(III) 1,4,7,10-tetraazacyclododecane N,N',N",N"'tetramethylenephosphonate (TmDOTP5-), and dysprosium(III)triethylenetetramine-hexaacetate (DyTTHA3-) are compared in this work for their uses in sodium chemical shift imaging (NaCSI). In a series of experiments using phantoms we evaluated the relative contributions of bulk magnetic susceptibility (BMS) effects and hyperfine shifts to the induced 23Na chemical shift for these two shift reagents. The ratios of BMS effects to hyperfine shifts suggest that TmDOTP5- should be a more effective shift reagent than DyTTHA3- for 23Na NMR spectroscopy as well as NaCSI. The dependence on pH and free Ca2+ concentration of the 23Na NMR frequency shift induced by TmDOTP5- was evaluated. It was found that TmDOTP5- produces good spectral resolution under physiologic conditions. Examples presented from in vivo NaCSI experiments using TmDOTP5- to study diffusion in the posterior chamber of the rabbit eye and to monitor the rate of clearance of aqueous fluid from the anterior chamber demonstrate the effectiveness of this new shift reagent and of the NaCSI technique for in vivo studies.

Aqueous shift reagents for high-resolution cation NMR spectroscopy. 4. [o-Bis((3-tripolyphosphato)propyloxy)benzene(-)]dysprosate(5-)

The chelate Dy(PPP) 2 7− (where PPP 5− is tripolyphosphate) is a very effective shift reagent for the 2 3Na NMR signal. However, it is also quite toxic to living animals. This paper reports the synthesis of the new shift reagent DybPPPpob 5− (where bPPPpob 8 − is o-bis((3-(tripolyphosphato)propyl)oxy)benzene). In vitro 23 Na and 31 P NMR experiments show that DybPPPpob 5− is an upfield shift reagent which shifts the 23 Na signal more than a third as well as Dy(PPP) 2 7− , competition by Ca 2+ and Mg 2+ with Na + for DybPPPpob 5− is not as severe as it is for Dy(PPP) 2 7− and DybPPPpob 5− hydrolysis is catalyzed by alkaline phosphatase but neither as rapidly nor as extensively as that of Dy(PPP) 2 7 −. This latter result implies that an uncoordinated PPP moiety of an incompletely dissociated DybPPPpob 5− chelate can still act as a substrate for the enzyme

Binuclear shift reagents for nuclear magnetic resonance spectrometry of aromatic and polycyclic aromatic compounds

The effects of adding binuclear lanthanide(III)-silver(I) shift reagents to aromatic compounds and phosphines are discussed. With aromatic compounds, the silver bonds at sites away from alkyl substituents so that selective shifts, leading to significant spectral clarification, are observed. Because of different shifts, the analysis of complex mixtures such as the methylbenzenes in gasoline can be performed in the presence of these shift reagents. A study of the relative shifting ability of the binuclear complexes formed with the ligand 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedione (fod), vs. 2,2,6,6-tetramethyl-3,5-heptanedione (thd), revealed that the fluorinated ligands are much more effective shift reagents.

Selective iron(II) phthalocyanine and ruthenium(II) phthalocyanine shift reagents

Some of the properties of the iron(II) phthalocyanine NMR shift reagents FePc, FePc(NH 2C 4H 9) 2, FePc(ND 2C 4D 9) 2, FePc(NH 2C 6H 5) 6, and FePc(ND 2C 6D 5) 6, and the ruthenium(II) phthalocyanine NMR shift reagents RuPc, RuPc[(CH 3) 2SO] 6, and RuPc[(CD 3) 2SO] 6 are described and commented on. The results of applying FePc, FePc(NH 2C 6H 5) 6, FePc(ND 2C 6D 5) 6, RuPc, RuPc[(CH 3) 2SO] 6, and RuPc[(CD 3) 2SO] 6 to a variety of compounds are given. It is concluded that FePc, FePc(NH 2C 6H 5) 6, and FePc(ND 2C 6D 5) 6 are effective shift reagents for a substantial range of imidazoles, pyridines, and primary aliphatic amines, and a narrow range of secondary aliphatic amines. It is also concluded that RuPc, RuPc[(CH 3) 2SO] 6, and RuPc[(CD 3) 2SO] 6 are effective shift reagents for a wide range of imidazoles, pyridines, primary aliphatic amines, and primary aromatic amines, a substantial range of secondary aliphatic amines, secondary aromatic amines, and hydrazines, and a narrow range of tertiary aliphatic amines. Factors which influence the applicability of the reagents are discussed.