According to the solid-state ¹³C, ³¹P NMR study and ¹³C chemical shift anisotropy (CSA) measurements, aromatic rings in the layered metal(IV) phosphonate materials behave as low-energy rotors at rotation activation energy, E_act, of 1.4–3.0 kcal/mol. The rotational mechanism consists of 180° flips and librations around C(1)–C(4) axis. The amplitude of the librations, added to the flips, grows with temperature, shifting the reorientations toward rotational diffusion at high temperatures.

中文翻译：

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层状Sn（IV）和Zr（IV）膦酸酯材料中芳环的平移和旋转运动：可变温度13C，31P固态NMR研究。

根据固态¹³ C，³¹ P NMR研究和¹³ C化学位移各向异性（CSA）测量，层状金属（IV）膦酸酯材料中的芳环在旋转活化能E _act为时表现为低能转子。 1.4–3.0 kcal / mol。旋转机构由围绕C（1）–C（4）轴的180°翻转和释放组成。释放的幅度加到翻转中，随温度增加而增加，从而使重定向在高温下向旋转扩散移动。