Observability of Paramagnetic NMR Signals at over 10 000 ppm Chemical Shifts

Ott, Jonas; Suturina, Elizaveta A.; Kuprov, Ilya; Nehrkorn, Joscha; Schnegg, Alexander; Enders, Markus; Gade, Lutz H.

doi:10.1002/anie.202107944

Cited by 18 publications

(18 citation statements)

References 86 publications

(138 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Visual comparison of the sensitivity of δ to temperature of 1 , 2 and 4 with 59 Co and other notable nuclei. Data were extracted from refs , –. Conditions under which these data were collected follow [Co(acac) 3 ]: 0.1 M in C 6 D 6 (65 MHz); 19 F–Fe: 2.1 M in H 2 O (400 MHz); 1 H-[( t Bu PNP)FeH]: toluene- d 8 (400 MHz); 31 P-[( t Bu PNP)FeH]: toluene- d 8 (200 MHz).…”

Section: Resultsmentioning

confidence: 99%

“…For example, the spin-crossover of Fe(II) complexes is applied to shifting ligand-based 19 F nuclei, but the sensitivities are relatively small (0.7 ppm/°C) . Separately, a recent pair of studies on 1 H and 31 P nuclei coordinated to Fe(III) exhibited a huge change in thermal sensitivities of the 1 H and 31 P chemical shifts, , 14 and 34 ppm/°C, respectively. In both these cases, interactions between the nuclei and the paramagnetic (or spin-crossover) ion are primarily through the pseudo-contact shift and Fermi contact contributions, − the latter less important when the nucleus of interest is spaced far from the metal ion.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Record Chemical-Shift Temperature Sensitivity in a Series of Trinuclear Cobalt Complexes

Üngör

Ozvat

et al. 2022

J. Am. Chem. Soc.

View full text Add to dashboard Cite

Designing spins that exhibit long-lived coherence and strong temperature sensitivity is central to designing effective molecular thermometers and a fundamental challenge in the chemistry/quantuminformation space. Herein, we provide a new pathway to both properties in the same molecule by designing a nuclear spin, which possesses a robust spin coherence, to mimic the strong temperature sensitivity of an electronic spin. This design strategy is demonstrated in the group of trinuclear Co(III) spin-crossover compounds [(CpCo(OP(OR) 2 ) 3 ) 2 Co](SbCl 6 ) where Cp = cyclopentadienyl and R = Me (1), Et (2), i-Pr (3), and t-Bu (4). Nuclear magnetic resonance analyses of the 59 Co nuclear spins reveal 59 Co chemical-shift temperature sensitivity (Δδ/ΔT) values that span from 101(1) ppm/°C in 1 to 149(1) ppm/°C in 2 and 150(2) ppm/°C in 4, where the latter two are record temperature sensitivities for any nuclear spin. Additionally, complexes 2 and 4 have T 2 * values of 74 and 78 μs in solution at ambient temperatures surpassing those from electron-spin-based complexes, which typically display long coherence times only at extremely low temperatures. Our results suggest that spin-crossover phenomena can enable electron-spin-like temperature sensitivities in nuclear spins while retaining robust coherence times at room temperature.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Record Chemical-Shift Temperature Sensitivity in a Series of Trinuclear Cobalt Complexes

Üngör

Ozvat

et al. 2022

J. Am. Chem. Soc.

View full text Add to dashboard Cite

show abstract

“…This mechanism called contact shift is operative in close vicinity to paramagnetic ions and can induce shifts as large as 10 000 ppm. 15 The pseudocontact shift (PCS, pseudocontact) is a long-range term (1/ r 3 ) from the electron–nucleus dipolar coupling and magnetic anisotropy of the paramagnetic center. Paramagnetic ions can induce PCS effects for NMR active nuclei at distances of 25–40 Å.…”

Section: Introductionmentioning

confidence: 99%

Electron correlation and vibrational effects in predictions of paramagnetic NMR shifts

Jaworski

Hedin

2022

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

show abstract

“…In addition, NMR is known to be adversely affected by the presence of paramagnetic species, such as free radicals. 37 On the other hand, ESR is a sensitive technique for free radicals, which are often observed in carbon materials, but it can only be used if free radicals are present. Finally, we used TGA to confirm product formation when the products change boiling point and thermal behaviors.…”

Section: Confirming Reactivities With Complementarymentioning

confidence: 99%

Unexpected Structural Effects on the Onset of Thermal Reactions of Aromatic Hydrocarbons

et al. 2023

View full text Add to dashboard Cite

This work aims to study the reactivity of a broad range of aromatic hydrocarbons to better understand the reactivities of more complex hydrocarbon mixtures. A set of closed-system pyrolysis experiments were conducted on a diverse range of ∼30 polycyclic aromatic hydrocarbons (PAHs) at the thermal onset reaction temperature of 400 °C to understand structural effects on reactivities and shed light on the early events of thermal reaction mechanisms. Thermal transformations, including methyl transfer (alkylation/dealkylation), rearrangement, condensation, molecular growth, and other chemical transformations, are often indicated by dark carbon materials composed of complex mixtures. Thermal transformation was confirmed by phenomenological changes (color and solubility) and chemical analysis using nuclear magnetic resonance, thermogravimetric analysis, gas chromatography, and electron spin resonance. Unsubstituted PAHs (e.g., phenanthrene, anthracene, pyrene, chrysene, etc.) were unaffected by heating at this temperature, with the exception of tetracene and pentacene which readily transformed into dark and insoluble materials. The reactivity of these unsubstituted PAHs is consistent with aromaticity predicted by the Clar theory. On the contrary, most alkyl-substituted PAHs can be transformed into carbon materials at 400 °C; however, alkyl-substituted phenanthrenes (2,7-dimethyl, 2-ethyl, or 7-ethyl) and benzenes (xylenes and pentamethylbenzene) were unreactive. CH2-containing PAH molecules were unreactive if in a five-membered ring (e.g., fluorene and benzofluorene) but became reactive if in a six-membered ring (9,10-dihydroanthracene), likely as a result of aromatization of the latter. The reactivity of the aryl–aryl linkage depends upon the aromatic moieties to which it is connected. While it is unreactive when connecting phenyl groups, such as in p-terphenyl, it is reactive when connecting pyrenes, such as in 1,1′-bispyrene. These results were unexpected and challenge the conventional thinking about hydrocarbon reactivities. Explanations and possible hypotheses are proposed, but more questions remain unanswered to understand the structural effects on reactivities. These findings are conducive to the sustainable use of aromatic hydrocarbons for higher value carbon materials and relevant to numerous pyrolysis studies on oil shale kerogens, biomass, and waste plastics.

show abstract

Observability of Paramagnetic NMR Signals at over 10 000 ppm Chemical Shifts

Cited by 18 publications

References 86 publications

Record Chemical-Shift Temperature Sensitivity in a Series of Trinuclear Cobalt Complexes

Record Chemical-Shift Temperature Sensitivity in a Series of Trinuclear Cobalt Complexes

Electron correlation and vibrational effects in predictions of paramagnetic NMR shifts

Unexpected Structural Effects on the Onset of Thermal Reactions of Aromatic Hydrocarbons

Contact Info

Product

Resources

About