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首页> 外文期刊>Chemistry: A European journal >Discrepancy between the spin distribution and the magnetic ground state for a triaminoxyl substituted triphenylphosphine oxide derivative
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Discrepancy between the spin distribution and the magnetic ground state for a triaminoxyl substituted triphenylphosphine oxide derivative

机译：三氨基甲酰基取代的三苯基膦氧化物衍生物的自旋分布与磁性基态之间的差异

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摘要

The magnetic interaction and spin transfer via phosphorus have been investigated for the tri-tert-butylaminoxyl para-substituted triphenylphosphine oxide. For this radical unit, the conjugation existing between the pi* orbital of the NO group and the phenyl pi orbitals leads to an efficient delocalization of the spin from the radical to the neighboring aromatic ring. This has been confirmed by using fluid solution high-resolution EPR and solid state MAS NMR spectroscopy. The spin densities located on the atoms of the molecule could be probed since H-1, C-13, N-14, and P-31 are nuclei active in NMR and EPR, and lead to a precise spin distribution map for the triradical. The experimental investigations were completed by a DFT computational study. These techniques established in particular that spin density is located at the phosphorus (p=-15 x 10(-3) au), that its sign is in line with the sign alternation principle and that its magnitude is in the order of that found on the aromatic C atoms of the molecule. Surprisingly, whereas the spin distribution scheme supports ferromagnetic interactions among the radical units, the magnetic behavior found for this molecule revealed a low-spin ground state characterized by an intramolecular exchange parameter of J = -7.55 cm(-1) as revealed by solid state susceptibility studies and low temperature EPR. The X-ray crystal structures solved at 293 and 30 K show the occurrence of a crystallographic transition resulting in an ordering of the molecular units at low temperature.
机译：已经研究了三叔丁基氨基二甲苯基对位取代的三苯基膦氧化物的磁性相互作用和通过磷的自旋转移。对于该自由基单元，存在于NO基团的pi *轨道与苯基pi轨道之间的共轭导致自旋从自由基到相邻芳环的有效离域。这已经通过使用流体溶液高分辨率EPR和固态MAS NMR光谱得到了证实。由于H-1，C-13，N-14和P-31在NMR和EPR中具有核活性，因此可以探测位于分子原子上的自旋密度，从而得出三基的精确自旋分布图。通过DFT计算研究完成了实验研究。这些技术特别确定了自旋密度位于磷（p = -15 x 10（-3）au）处，其符号与符号交替原理一致，并且其大小与在磷上的数量级相同。分子的芳族碳原子。出乎意料的是，尽管自旋分布方案支持自由基单元之间的铁磁相互作用，但该分子的磁性行为揭示了低自旋基态，其分子内交换参数为J = -7.55 cm（-1），如固态所揭示药敏试验和低温EPR。在293和30 K下解析的X射线晶体结构显示出晶体学转变的出现，导致低温下分子单元的排序。

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