ESR study of molecular dynamics and orientation of TEMPO included in organic 1-D nanochannel
ESR study of molecular dynamics and orientation of TEMPO included in organic 1-D nanochannel
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DOI：
10.1039/b710098a
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发表时间：
2008-01-01
影响因子：
3.3
通讯作者：
Tani, Atsushi
中科院分区：
文献类型：
--
作者：
Kobayashi, Hirokazu;Ueda, Takahiro;Tani, Atsushi
将2,2,6,6-四甲基-1-胡椒酰氧基（TEMPO）自由基和2,2,6,6-四甲基-1-胡椒啶（TEMP）的混合物加入到三（邻苯二氧基）环三磷腈（TPP）晶体的有机1-D纳米通道中。顺磁性TEMPO自由基被过量的温度稀释，从而在纳米通道中分离出TEMPO分子。对于TEMPO和TEMP的TPP包合物(TEMPO/所有客体化合物分别为0.017(1)和0.15(2))，通过观察温度相关的电子自旋共振（ESR）光谱来研究其分子动力学和取向。在112 K至室温范围内，光谱与温度有显著的相关性。单轴旋转很好地解释了温度依赖性，表明TEMPO分子沿通道轴进行单轴旋转，其分子取向是氮氧化物基团中的N-O键垂直于通道轴。单轴旋转活化能为4.5 +/- 0.3 kJ mol（-1）。
A mixture of 2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO) radical and 2,2,6,6-tetramethyl-1-piperidine (TEMP) was included into organic 1-D nanochannels of tris(o-phenylenedioxy) cyclotriphosphazene (TPP) crystal. Dilution of the paramagnetic TEMPO radical was achieved with excess TEMP, thereby isolating a TEMPO molecule in the nanochannel. For inclusion compounds of TPP with TEMPO and TEMP (TEMPO/all guest compounds = 0.017 (1), and 0.15 (2)), temperature-dependent electron spin resonance (ESR) spectra were observed to investigate their molecular dynamics and orientation. In the temperature range from 112 K to room temperature, the spectra depended remarkably on the temperature. Temperature dependence was well interpreted by uniaxial rotation, suggesting that TEMPO molecules undergo uniaxial rotation about a channel axis with a molecular orientation in which the N-O bond in the nitroxide group is perpendicular to the channel axis. The activation energy of uniaxial rotation was evaluated as 4.5 +/- 0.3 kJ mol(-1).