骨架金属原子对Keggin阴离子电子结构和物化性质的研究

使用第一原理密度泛函理论中的离散变分方法(DFT-DVM)对(PM~1~2O~4~0)^n^-(M=Mo,W,V),(PMo~9W~3O~4~0)^3^-,(PMo~9V~3O~4~0)^6^-五种Keggin结构杂多阴离子进行了电子结构计算,讨论了骨架金属原子对Keggin结构杂多阴离子的电荷分布、成键作用、热稳定性、氧化还原性等的影响。结果表明,骨架金属原子对Keggin阴离子的电荷分布和成键作用均有一定的影响,以Mo,W,V作骨架金属原子的Keggin阴离子(PM~1~2O~4~0)^n^-的热稳定性顺序为:(PW~1~2O~4~0)~3^->(PMo~1~2O~4~0)^3^->(PV~1~2O~4~0)^1^5^-。提出了判断杂多阴离子氧化性强弱的两因素法---脱出晶格氧的难易程度和LUMO轨道电负性,并根据两因素法得到氧化性强弱顺序为:(PV~1~2O~4~0)^1^5^->(PMo~1~2O~4~0)^3^->(PW~1~2O~4~0)~3^-。同时,讨论了当(PMo~1~2O~4~0)~3^-中的Mo部分被W和V取代后,即(PMo~9W~3O~4~0)^3^-,(PMo~9V~3O~4~0)^6^-,其中取代原子对电子结构的影响,结果表明,W取代使整个阴离子的稳定性增强,但氧化性减弱,V取代,使稳定性减弱,但氧化性增强。

The influences of skeleton metal atoms on electronic structures and physical-chemistry properties of Keggin anions

The electronic structures of Keggin anions (PM12O40)n- (M = Mo, W, V) ,(PMo9W3O40)3-(PMo9V3O40)6- have been calculated by the Discrete Variational Method coupled with the first principal Density Functional Theory (DFT- DVM). The influences of skeleton metal atoms on the charge distribution, bonding effects, stability, redox properties are discussed. The results show that skeleton metal atoms have influence on the charge distribution and bonding effects. The relative sequence of stability is: (PW12O40)3- > (PMo12O40)3- > (PV12O40)15-. We developed the two- factors method for determining the escape ability of lattice oxygen atoms and the LUMO electronegativity. The relative sequence of redox properties has then been shown to be: (PV12O40)15- > (PMo12O40)3-> (PW12O40)3-. The replacement effects of Mo with W and V are discussed. The stability of Keggin units is strengthened, but the redox ability is weakened when the Mo atoms are replaced by W. The stability is weakened and redox property is strengthened when the Mo atoms are replaced by V.