Anomalous Magnetic Properties of Molecular Oxygen Adsorbed in Microporous Metal-Organic Solids

分子氧在CPL-1[Cu2(Pzdc)2(PYZ)]的配位空间中形成02-02二聚体。研究发现，02的排列不仅与客体分子与主体分子之间的相互作用有关，而且与分子间的相互作用有关。02-02二聚体的从头计算指出，磁相互作用有助于形成单重态(S=0)的H结构排列，而四重态(S=2)的最稳定排列是不同的。因此，我们对凝聚的02体系的场诱导重排进行了一般的预测。在本项目中，我们通过X射线粉末衍射和磁性测量的方法研究了吸附在配位空间中的02的排列与磁性之间的关系。在CPL-1的情况下，磁化过程和磁化率的温度依赖关系可以通过考虑不同分子排列的激发态来解释。在吸附在铜-CHD[铜-1，4-环己二元酸]中的02中也观察到了类似的磁性。虽然MEM/Rietvelt分析正在进行中，以确定吸附的O2的排列，但观察到的磁性可以用相同的模型解释。在CPL-p1[Cu(Dhba)2(4，4‘-bpy)]和CID-4[Cd(Bpndc)(Bpy)]中，吸附的O2的磁化过程表现出依赖于吸附的变磁转变。虽然02的排列不清楚，但很明显，这些化合物中的配位空间比CPL-1或铜-CHD的配位空间大。自然而然地认为，少数几个吸附中心的存在导致了吸附依赖，到目前为止，对场诱导重排的直接观察并不成功。对于CPL-1，临界电场太高，不能进行X射线衍射实验。对于临界场较低的铜-CHD，可望通过X射线衍射仪观察到场诱导重排现象。

Molecular oxygen forms 02-02 dimer in the coordination space of CPL-1 [Cu2(pzdc)2(pyz)]. It is found that the arrangement of 02 is associated not only with the interaction between the guest molecules and the host compound but also with the intermolecular interaction. The ab initio calculation of 02-02 dimer has pointed out that the magnetic interaction contributes to the formation of the H-structure alignment with singlet ground state (S = 0) while the most stable alignment of the quartet state (S = 2) is known to be different. Therefore we predicted the field-induced rearrangement in condensed 02 system in general.In this project, we have investigated the relation between the arrangement and the magnetic properties of 02 adsorbed in the coordination space by means of x-ray powder diffraction and magnetic measurements. In the case of CPL-1, the magnetization process and the temperature dependence of susceptibility can be interpreted by considering the excited state with different molecular arrangements. Similar magnetic properties have been observed in 02 adsorbed in Cu-CHD [Cu-1,4-cyclohexanedicarboxylic acid]. Though the MEM/Rietvelt analysis to determine the arrangement of adsorbed 02 is now in progress, the observed magnetic properties can be explained by same model. In CPL-p1 [Cu(dhba)2(4,4' -bpy)] and CID-4 [Cd(bpndc) (bpy)], the magnetization processes of adsorbed 02 show the metamagnetic transitions which depends on the adsorption. Though the arrangement of 02 is not clear, it is clear that the coordination spaces in these compounds are larger than that of CPL-1 or Cu-CHD. It is naturally considered that the existence of a few adsorption sites causes the adsorption dependence.Up to now the direct observation of field-induced rearrangement has not been succeeded. For CPL-1, the critical field is too high to carry out the XRD experiment. For Cu-CHD with lower critical field, the observation of field-induced rearrangement by XRD measurement is expected.