【摘要】 合成了新型杂多阴离子二聚体K₁₂(SiMW₁₁O₃₉)₂O·29H₂O(简写为(SiMW₁₁)₂O,M=Fe^Ⅱ,Cr^Ⅱ,Al^Ⅲ),并用元素分析、红外及电子光谱等进行了表征。其中(SiCrW₁₁)₂O及(SiAlW₁₁)₂O未见文献报导。用XPS测定了M_2p的结合能,结果表明:与SiMW₁₁相比,(SiMW₁₁)₂O中M_2p结合能偏低0.7～0.9ev,结合红外及紫外光谱,可以推测,二聚体中两个杂多阴离子以M-O-M桥氧相连。其中氧的2p轨道与M的3d轨道重叠形成了d-pπ键。二聚体(SiFeW₁₁)₂O及(SiCrW₁₁)₂O中Fe^Ⅱ,Cr^Ⅱ的有效磁矩比单体明显偏低,表明铁、铬桥氧键中两个金属原子M^Ⅱ的d电子通过桥氧发生了反磁性交换。更多还原

【Abstract】 Heteropoly anion dimers K₁₂(SiW₁₁O₃₉)₂·29H₂O(abbreviated to (SiMW₁₁)₂O, M = Fe^Ⅲ, Cr^Ⅱ , and Al^Ⅱ) were prepared, and characterized by element analysis, IR and UV. The binding energies of M_2p in anions were determined by XPS. The results show that M_2p, binding energies in (SiMW₁₁)₂O are 0.7-0.9 eV lower than those in SiMW₁₁. From the M_2p binding energies, IR and UV, it is deduced that two heteropoly anions in the dimers are connected by M-O-M, in which 2p orbits of OXO-bridged oxygen may be overlapped with 3d orbits of metal M^Ⅱ to form d-pπ bonds. The magnetic susceptibility of Fe and Cr in (SiFeW₁₁)₂O and (SiCrW₁₁)₂O is obviously lower than those in SiFeW₁₁ and SiCrW₁₁. This means that there is an antimagnetic exchange of d electrons between two M^Ⅱ through the bridged oxygen.更多还原