Within the present contribution, we describe solid-state NMR spectroscopic studies of the paddle wheel unit in the prototypic flexible MOF compound DUT-8(M) (M = Ni, Co, Zn). The ¹³C NMR chemical shift of these carboxylates shows a remarkable behavior. The pure 2,6-H₂ndc linker carboxylates as well as DUT-8(Zn) exhibit a¹³C chemical shift of only about 170 ppm. In contrast, much higher values are observed for DUT-8(Ni) and especially DUT-8(Co). In the open pore state, the shift strongly depends on the solvent polarity in these two latter cases. The present contribution elucidates the reason for this solvent influence. It is concluded that the solvent mainly modifies the isotropic Fermi contact coupling constant for the excited high-spin states in DUT-8(Ni) and DUT-8(Co).

在目前的贡献中，我们描述了原型柔性 MOF 化合物 DUT-8（M）（M = Ni、Co、Zn）中桨轮单元的固态 NMR 光谱研究。这些羧酸盐的¹³ C NMR 化学位移表现出显着的行为。纯 2,6-H ₂ ndc 连接剂羧酸盐以及 DUT-8(Zn) 表现出¹³C化学位移仅为约170 ppm。相比之下，对于 DUT-8(Ni)，尤其是 DUT-8(Co)，观察到的值要高得多。在开孔状态下，在后两种情况下，这种转变很大程度上取决于溶剂极性。目前的贡献阐明了这种溶剂影响的原因。得出的结论是，溶剂主要改变了 DUT-8(Ni) 和 DUT-8(Co) 中激发的高自旋态的各向同性费米接触耦合常数。