Frequency dependence of electron spin relaxation times in aqueous solution for a nitronyl nitroxide radical and perdeuterated-tempone between 250 MHz and 34 GHz.
Frequency dependence of electron spin relaxation times in aqueous solution for a nitronyl nitroxide radical and perdeuterated-tempone between 250 MHz and 34 GHz.
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DOI：
10.1016/j.jmr.2012.10.002
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发表时间：
2012-12
影响因子：
2.2
通讯作者：
Eaton, Gareth R.
中科院分区：
文献类型：
--
作者：
Biller, Joshua R.;Meyer, Virginia M.;Elajaili, Hanan;Rosen, Gerald M.;Eaton, Sandra S.;Eaton, Gareth R.
用二脉冲电子自旋回波（T2）和三脉冲反转恢复（T1）测量了全氘代丁酮（PDT）1和硝基氮氧自由基（2-（4-羧基苯基）-4，4，5，5-四甲基咪唑啉-3-氧化物-1-氧基）2在室温水溶液中的电子自旋弛豫时间。在9 GHz的值T1测量的长脉冲饱和恢复与反演恢复确定的值吻合良好。对于1，低于9 GHz，对于2，低于1.5 GHz，T1~ T2，如在快速翻滚状态中所预期的。在较高的频率T2短于T1由于不完全的运动平均的g和A的各向异性。1/T1的频率依赖性被建模为自旋旋转，g和A-各向异性的调制，以及在约1.5 GHz处具有最大贡献的热激活过程的总和。硝酰基氮氧化物的自旋晶格弛豫时间在34 GHz下比PDT长约2倍，在250 MHz下降低至约1.5倍。旋转相关时间τR被计算为对于1为9 ps，对于2为约25 ps。较长的自旋晶格弛豫时间为2比1在9和34 GHz的主要是由于较小的贡献，从自旋旋转所产生的较慢的翻滚。硝酰基2的氮超精细耦合比1减少的贡献，由于A各向异性的调制弛豫。然而，在较低频率下，2的较慢翻转导致ωτR（ω是共振频率）的较大值和谱密度函数的较大值，这将2的各向异性相互作用的调制的贡献增强到比1更大的程度。
Electron spin relaxation times of perdeuterated tempone (PDT) 1 and of a nitronyl nitroxide 2-(4-carboxy-phenyl)-4,4,5,5-tetramethylimidazoline-3-oxide-1-oxyl) 2 in aqueous solution at room temperature were measured by 2-pulse electron spin echo (T2) or 3-pulse inversion recovery (T1) in the frequency range of 250 MHz to 34 GHz. At 9 GHz values of T1 measured by long-pulse saturation recovery were in good agreement with values determined by inversion recovery. Below 9 GHz for 1 and below 1.5 GHz for 2, T1~ T2, as expected in the fast tumbling regime. At higher frequencies T2 was shorter than T1 due to incomplete motional averaging of g and A anisotropy. The frequency dependence of 1/T1 is modeled as the sum of spin rotation, modulation of g and A-anisotropy, and a thermally-activated process that has maximum contribution at about 1.5 GHz. The spin lattice relaxation times for the nitronyl nitroxide were longer than for PDT by a factor of about 2 at 34 GHz, decreasing to about a factor of 1.5 at 250 MHz. The rotational correlation times, τR are calculated to be 9 ps for 1 and about 25 ps for 2. The longer spin lattice relaxation times for 2 than for 1 at 9 and 34 GHz are due predominantly to smaller contributions from spin rotation that arise from slower tumbling. The smaller nitrogen hyperfine couplings for the nitronyl 2 than for 1 decrease the contribution to relaxation due to modulation of A anisotropy. However, at lower frequencies the slower tumbling of 2 results in a larger value of ωτR (ω is the resonance frequency) and larger values of the spectral density function, which enhances the contribution from modulation of anisotropic interactions for 2 to a greater extent than for 1.
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影响因子：
3.3
作者：
Hyde, JS;Yin, JJ;Froncisz, W
通讯作者：
Froncisz, W
影响因子：
2.9
作者：
Mailer, C;Nielsen, RD;Robinson, BH
通讯作者：
Robinson, BH
影响因子：
1.6
作者：
QUINE, RW;EATON, GR;EATON, SS
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影响因子：
15
作者：
Barone, Vincenzo;Brustolon, Marina;Zoleo, Alfonso
通讯作者：
Zoleo, Alfonso
DOI：
10.1073/pnas.79.8.2559
发表时间：
1982-01-01
期刊：
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA-BIOLOGICAL SCIENCES
影响因子：
--
作者：
POPP, CA;HYDE, JS
通讯作者：
HYDE, JS