Preparation of high densitivity and resolution solid state NMR probe for transition metal nuclei

在低共振频率区有许多有用的原子核。但由于其灵敏度较低，对其固态核磁共振谱的研究很少。为了克服高分辨率固态MAS核磁共振谱测量的困难，我们制备了一种高灵敏度的低共振频率（低伽马）和半整数自旋核探针。特别是Ag-109核磁共振探针在银类化合物的材料科学研究中具有重要的应用价值。准备探针的要点如下。(1)根据Hartman-Hahn条件，CP时间比通常的C-13实验要长得多，为50-100 ms。除此之外，应用的领域比C-13的情况下强得多。因此，探头应长时间在高功率下工作。(2)为了在子弹样管中填充更大的样品量，增大线圈直径。(3)针对上述条件对探头电路进行了改进。在此基础上，我们制备了一种探针，并成功地以高灵敏度测量了各种银化合物的Ag-109光谱。采用[Ag（2,9-菲罗啉）2]PF6检测CPMAS条件。得到了信号强度与接触时间的关系图，以供实际使用。在接触时间t=50 ms时获得了最大强度，测量了从单核到配位聚合物的各种银化合物的光谱。我们发现[Ag（二羟基苯醌）]n是在短时间内获得强信号的最佳化合物，因为它的距离为109Ag…1H。除了测量技术外，我们还完成了依赖于配体供体原子的化学位移方案。位移范围从0 ppm到1000 ppm。用线性型的吡啶衍生物银化合物讨论了化学位移的来源。这种转变趋势表明，西格玛和pi机制是相互竞争的。

There are many useful nuclei in low resonance frequency region. However, few studies of their solid state NMR spectra have been reported because of their low sensitivity. In order to overcome the difficulties in measurements of high resolution solid state MAS NMR spectra, We have prepared a high sensitive probe for nuclei having low resonance frequency (low-gamma) and half-integer spin. Especially, Ag-109 NMR probe is useful for material science of silver compounds. The important points to prepare the probe are as follows. (1) According to Hartman-Hahn condition, the CP time is much longer than that in usual C-13 experiments, 50-100 ms. In addition to this, the applied field is much stronger than that of C-13 case. Thus, the probe should work against high power for long time. (2) To fill larger amount of sample in a bullet sample tube, the coil diameter is enlarged. (3) The probe circuits are improved in response to the above conditions. On these basis we have prepared a probe and succeeded in measuring Ag-109 spectra of various silver compounds with high sensitivity. The CPMAS conditions was checked by using [Ag(2,9-phenanthroline)2]PF6. The plots of signal intensity vs. contact time were obtained for practical use. The maximum intensity was obtained at a contact time, t=50 ms.The spectra were measured for various Ag compounds from mononuclear to coordination polymers. We found that[Ag(dihydroxybenzoquinone dianion)]n is the best compound to obtain a strong signal within a short time due to its shortest distance of 109Ag...1H.In addition to the know-how for the measurements we have completed chemical shifts scheme depending on donor atoms of ligands. The shift ranges from 0 ppm to 1000 ppm. the origin of the chemical shift was also discussed by using linear type silver compounds of pyridine derivatives. The shift trend shows that sigma-andpi-mechanism are competing.