中文摘要：

采用DFT-BS方法研究异双核的Keggin型杂多酸衍生物[M（H2O）XW11O39]7-（Ⅰ： X=FeⅢ, M=CoⅡ; Ⅱ： X=CoⅢ, M=CoⅡ）的磁耦合作用, 计算得到耦合常数（J）为负值, 表明所研究体系具有反铁磁性; J值大小顺序为｜J（Ⅰ）｜〈｜J（Ⅱ）｜, 说明磁耦合作用增强; 体系Ⅰ与Ⅱ相比, X由FeⅢ变成CoⅢ, M不变, 桥氧原子Ob和Ob2（O′b2）上的自旋密度增大, 进一步从相关BS态的磁轨道比较得出, 体系Ⅱ中轨道重叠程度大于体系Ⅰ, 结果使X-M之间的反铁磁耦合作用加强.

英文摘要：

The magnetic exchange interactions for the biheteroatom 11-heteropoly complexes ： [M（H2O）XW11O39]7-（X=Fe^Ⅲ, Co^Ⅲ; M=Co^Ⅱ） were investigated via density functional theory combined with broken-symmetry approach（DFT-BS） method. The calculated J values are - 35 cm^- 1 （ Ⅰ ） and - 44 cm^- 1 （ Ⅱ ）, respectively, which show that antiferromagnetie exchange interactions exist in these complexes. The order of the absolute value of J is ： ｜ J（ I ） ｜ 〈 ｜ J（ Ⅱ ） ｜ , indicating the increase of coupling interaction from system Ⅰ to Ⅱ. With the change of the heteroatom X via Fe^Ⅱ （ Ⅰ ）→Co^Ⅲ （ Ⅱ ）, the spin densities on bridge oxygen atoms Ob and Ob2 （O＇b2） increase. Furthermore, from the comparison of BS magnetic orbitals in system Ⅰ and Ⅱ we find the overlap of relative orbitals in system Ⅱ enlarges. Consequently, a stronger antiferromagnetic coupling arises in system Ⅱ than in Ⅰ.