Dataset Information

Spin-crossover and high-spin iron(ii) complexes as chemical shift ¹⁹F magnetic resonance thermometers.

ABSTRACT: The potential utility of paramagnetic transition metal complexes as chemical shift ¹⁹F magnetic resonance (MR) thermometers is demonstrated. Further, spin-crossover Fe^II complexes are shown to provide much higher temperature sensitivity than do the high-spin analogues, owing to the variation of spin state with temperature in the former complexes. This approach is illustrated through a series of Fe^II complexes supported by symmetrically and asymmetrically substituted 1,4,7-triazacyclononane ligand scaffolds bearing 3-fluoro-2-picolyl derivatives as pendent groups (L _x ). Variable-temperature magnetic susceptibility measurements, in conjunction with UV-vis and NMR data, show thermally-induced spin-crossover for [Fe(L₁)]²⁺ in H₂O, with T_1/2 = 52(1) °C. Conversely, [Fe(L₂)]²⁺ remains high-spin in the temperature range 4-61 °C. Variable-temperature ¹⁹F NMR spectra reveal the chemical shifts of the complexes to exhibit a linear temperature dependence, with the two peaks of the spin-crossover complex providing temperature sensitivities of +0.52(1) and +0.45(1) ppm per °C in H₂O. These values represent more than two-fold higher sensitivity than that afforded by the high-spin analogue, and ca. 40-fold higher sensitivity than diamagnetic perfluorocarbon-based thermometers. Finally, these complexes exhibit excellent stability in a physiological environment, as evidenced by ¹⁹F NMR spectra collected in fetal bovine serum.

SUBMITTER: Thorarinsdottir AE

PROVIDER: S-EPMC5477811 | biostudies-literature | 2017 Mar

REPOSITORIES: biostudies-literature

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Spin-crossover and high-spin iron(ii) complexes as chemical shift 19F magnetic resonance thermometers.

Thorarinsdottir Agnes E AE Gaudette Alexandra I AI Harris T David TD

Chemical science 20170106 3

The potential utility of paramagnetic transition metal complexes as chemical shift 19F magnetic resonance (MR) thermometers is demonstrated. Further, spin-crossover FeII complexes are shown to provide much higher temperature sensitivity than do the high-spin analogues, owing to the variation of spin state with temperature in the former complexes. This approach is illustrated through a series of FeII complexes supported by symmetrically and asymmetrically substitu ...[more]

PMID: 28694955

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Project description:PurposeA multiecho, field of view (FOV)-oversampled k-t spiral acquisition and direct iterative decomposition of water and fat with echo asymmetry and least-squares estimation reconstruction is demonstrated to improve the stability of hyperpolarized 13 C magnetic resonance spectroscopic imaging (MRSI) in the presence of signal ambiguities attributed to low-SNR (signal-to-noise-ratio) species, local uncertainties in metabolite peaks, and echo-to-echo signal inconsistencies.Theoryk-t spiral acquisitions redistribute readout points to be more densely spaced radially in k-space by acquiring an FOV and matrix that are oversampled by η. These more densely spaced spiral turns constitute effective intraspiral echoes and can supplement conventional interspiral echoes to improve spectral separation and reduce spectral cross-talk to better resolve 13 C-labeled species for spectroscopic imaging.MethodsDigital simulations and imaging phantom experiments were performed for a range of interspiral echo spacings and η using multiecho, k-t spiral acquisitions. Image spectral cross-talk artifacts were evaluated both qualitatively and quantitatively as the percent error in measured metabolite ratios. In vivo murine experiments evaluated the feasibility of multiecho, k-t spiral [1-13 C]pyruvate MRSI to reduce spectral cross-talk for 3 scenarios of different expected reconstruction stability.ResultsDigital simulations and imaging phantom experiments both demonstrated reduced or comparable image spectral cross-talk and percent errors in measured metabolite ratios with increasing η and better choices of echo spacings. In vivo images displayed markedly reduced spectral cross-talk in lactate images acquired with η = 7 versus η = 1.ConclusionThe precision of hyperpolarized 13 C metabolic imaging and quantification in the presence of low-SNR species, local uncertainties in metabolite resonances, and echo-to-echo signal inconsistencies can be improved with the use of FOV-oversampled k-t spiral acquisitions.

Dataset Information

Spin-crossover and high-spin iron(ii) complexes as chemical shift ¹⁹F magnetic resonance thermometers.

Publications

Spin-crossover and high-spin iron(ii) complexes as chemical shift <sup>19</sup>F magnetic resonance thermometers.

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