Nitrogen nuclear magnetic resonance spectroscopy in inorganic, organometallic, and bioinorganic chemistry

Mason, Joan

doi:10.1021/cr00043a001

Cited by 180 publications

(106 citation statements)

References 56 publications

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“…This phenomenon is analogous to that being the result of protonation of azines and azoloazines, where the diamagnetic shifts are of a similar or even higher magnitude (80-150 ppm). 27,28 We have recently described an analogous phenomenon for the Pd(II), Pt(II) and Pt(IV) chloride complexes of 1 and 2. 13,17 The coordination shifts also concerned N-3 and were even larger: Pd(II) 78-90 ppm, Pt(II) 92-93 ppm and Pt(IV) 94-96 ppm.…”

Section: Nmr Measurementsmentioning

confidence: 74%

¹H{¹⁵N} GHMQC study of 5,7‐diphenyl‐1,2,4‐triazolo[1,5‐a]pyrimidine and ¹H, ¹³C and ¹⁵N NMR coordination shifts in Au(III) chloride complexes of 1,2,4‐triazolo[1,5‐a]pyrimidines

Szłyk

Pazderski

Łakomska

et al. 2002

Magnetic Reson in Chemistry

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Section: Nmr Measurementsmentioning

confidence: 74%

¹H{¹⁵N} GHMQC study of 5,7‐diphenyl‐1,2,4‐triazolo[1,5‐a]pyrimidine and ¹H, ¹³C and ¹⁵N NMR coordination shifts in Au(III) chloride complexes of 1,2,4‐triazolo[1,5‐a]pyrimidines

Szłyk

Pazderski

Łakomska

et al. 2002

Magnetic Reson in Chemistry

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“…The computed absolute magnetic shieldings σ were finally converted into chemical shifts δ by applying the empirically determined linear equation δ = 200.65 − 1.0715σ for 13 C, [9] and the equation δ = −135.8 − σ based on the absolute nuclear shielding scale for nitrogen. [10] Comparison of the calculated structural parameters and shieldings for 2 in DMSO solution and in the gas phase revealed only very moderate changes (standard deviation of chemical shifts 3.2 ppm), thus justifying that the influence of different solvent polarity was further neglected in the calculations.…”

Section: Methodsmentioning

confidence: 94%

A solid state and solution NMR study of the tautomerism in hydroxyquinoline carboxylic acids

2008

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Some hydroxyquinoline carboxylic acids and their conjugate acids and bases were characterized by 13C and 15N NMR spectroscopy in solution and in the solid state. Differences in 13C and, in particular, 15N chemical shift patterns allow to distinguish between individual tautomers and confirm the presence of zwitterionic species in the solid state. Solution NMR spectra in dimethyl sulfoxide (DMSO) show effects resulting as a consequence of dynamic exchange and suggest the presence of an equilibrium mixture of hydroxyquinoline carboxylic acid and zwitterionic hydroxyquinolinium carboxylate tautomers.

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“…The remaining discrepancies are attributed to other relaxation mechanisms. Even slower singlet relaxation is expected for suitable larger molecules, for which even the conventional 15 N T 1 may be as long as 500 s. 14 We are now exploring the dependence of the 15 N 2 O singlet relaxation time on the solvent and the concentration of paramagnetic agents. For example, we have observed a T S of ∼19 min for 15 N 2 O in undegassed olive oil.…”

mentioning

confidence: 99%

The Long-Lived Nuclear Singlet State of ¹⁵N-Nitrous Oxide in Solution

et al. 2008

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Nuclear singlet states may have lifetimes T S that exceed the conventional magnetization relaxation time T 1 by an order of magnitude. [1][2][3][4][5][6][7][8][9][10][11] Applications of these states to the NMR measurements of slow molecular diffusion, chemical exchange, and the transportofhyperpolarizednuclearspinorderhavebeendemonstrated. [8][9][10][11] So far, long-lived nuclear singlet states have only been observed for proton pairs. We now demonstrate an extraordinarily long lifetime (T S ) of ∼26 min for the nuclear spin singlet of 15 N 2 -nitrous oxide (dinitrogen monoxide, N 2 O) in solution. This result has high potential importance since nitrous oxide is soluble in many important fluids such as water, oil, and blood. It is used routinely as a food additive, a gas propellant, and an anesthetic.Doubly labeled 15 N 2 O gas, purchased from CK-gas (UK), was dissolved in a degassed solution of DMSO-d 6 at a pressure of ∼3. Figure 1a.The slow relaxation of singlet states is revealed by suppressing their interconversion with the triplet states, either by using a resonant radiofrequency field [3][4][5][6] or by reducing the static magnetic field to a very low value. 1,2 The radiofrequency method is not feasible for The spin system is allowed to reach thermal equilibrium, and two strong 90°pulses with a relative phase of 90°are applied at the mean chemical shift frequency of the two 15 N sites. The delay between the pulses, τ 1 ) 0.198 ms, was chosen so that the transverse magnetization vectors of the two 15 N sites precess through 180°r elative to each other. The two pulses act as a selective 180°pulse on one of the 15 N sites and lead to a spin density operator 10 of the formwhere the two sites are denoted j and k and the selective inversion is assumed to act on site j. In this and the following equations, the subscript refers to a time point in Figure 2. The sample is transported out of the magnetic field by activating a stepper motor to wind up a string attached to the sample holder. The transport process takes τ tr ) 40 s and transports the sample into a region of low magnetic field, B low ≈ 2 mT, estimated by a Hall effect device. As shown in ref 2, slow adiabatic transport converts the population of each high-field state into that of the corresponding low-field state, leading to a density operator of the formwhere the low-field eigenstates areThe sample is left in the low-field region for a variable time τ LF . During the first few minutes, the three triplet populations equilibrate with each other on a time scale set by the relaxation constant T 1 . The density operator after several minutes in low magnetic field is therefore given approximately byThe sample is transported back into the high-field region by running the stepper motor in the opposite direction. Adiabatic transport from the density operator in eq 3 leads to

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Nitrogen nuclear magnetic resonance spectroscopy in inorganic, organometallic, and bioinorganic chemistry

Cited by 180 publications

References 56 publications

¹H{¹⁵N} GHMQC study of 5,7‐diphenyl‐1,2,4‐triazolo[1,5‐a]pyrimidine and ¹H, ¹³C and ¹⁵N NMR coordination shifts in Au(III) chloride complexes of 1,2,4‐triazolo[1,5‐a]pyrimidines

¹H{¹⁵N} GHMQC study of 5,7‐diphenyl‐1,2,4‐triazolo[1,5‐a]pyrimidine and ¹H, ¹³C and ¹⁵N NMR coordination shifts in Au(III) chloride complexes of 1,2,4‐triazolo[1,5‐a]pyrimidines

A solid state and solution NMR study of the tautomerism in hydroxyquinoline carboxylic acids

The Long-Lived Nuclear Singlet State of ¹⁵N-Nitrous Oxide in Solution

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Nitrogen nuclear magnetic resonance spectroscopy in inorganic, organometallic, and bioinorganic chemistry

Cited by 180 publications

References 56 publications

1H{15N} GHMQC study of 5,7‐diphenyl‐1,2,4‐triazolo[1,5‐a]pyrimidine and 1H, 13C and 15N NMR coordination shifts in Au(III) chloride complexes of 1,2,4‐triazolo[1,5‐a]pyrimidines

1H{15N} GHMQC study of 5,7‐diphenyl‐1,2,4‐triazolo[1,5‐a]pyrimidine and 1H, 13C and 15N NMR coordination shifts in Au(III) chloride complexes of 1,2,4‐triazolo[1,5‐a]pyrimidines

A solid state and solution NMR study of the tautomerism in hydroxyquinoline carboxylic acids

The Long-Lived Nuclear Singlet State of 15N-Nitrous Oxide in Solution

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¹H{¹⁵N} GHMQC study of 5,7‐diphenyl‐1,2,4‐triazolo[1,5‐a]pyrimidine and ¹H, ¹³C and ¹⁵N NMR coordination shifts in Au(III) chloride complexes of 1,2,4‐triazolo[1,5‐a]pyrimidines

¹H{¹⁵N} GHMQC study of 5,7‐diphenyl‐1,2,4‐triazolo[1,5‐a]pyrimidine and ¹H, ¹³C and ¹⁵N NMR coordination shifts in Au(III) chloride complexes of 1,2,4‐triazolo[1,5‐a]pyrimidines

The Long-Lived Nuclear Singlet State of ¹⁵N-Nitrous Oxide in Solution