摘要
使用SCC-DV-X_α方法计算了Keggin结构的杂多阴离子(SiMo_(12)O_(40))^(4-),(GeMo_(12)O_(40))^(4-),(AsMo_(12)O+(40))^(3-)的电子结构,并与文献对(PMo_(12)O_(40))^(3-)的计算结果作了对比分析.讨论了中心原子对Keggin结构的杂多阴离子的电子结构和催化性质的影响.结果表明,中心原子对Kegginn结构杂多阴离子的电子云、静电势、总态密度的分布影响不明显;但中心原子不同,前线轨道HOMOLUMO的组成有一些差异.四种阴离子的ε_(LUMO)和ε_(Fermi)的相对大小关系为:(AsWo_(12)O_(40))^(3-)>(PMo_(12)-O_(40))^(3-)>(GeMo_(12)O_(40))^(4-)>(SiMo_(12)O_(40))^(4-),其氧化能力和催化活性也具有相同的顺序.(XMo_(12)-O_(40))^(n-)(X=Si,Ge,P)中端氧O_(t),桥氧O_b,Mo以及X都具有催化活性,在催化反应中都可能成为催化活性中心,而(AsMo_(12)O_(40))^(3-)中仅有As和O_b可作为催化活性中心.
The electronic structures of Keggin-type heteropolyanions (SiMo12O40)4, (GeMo12-O40)4- and (AsMo12O40)3- have been calculated by the SCC-DV-Xa method. According to the comparison among calculating results of the three heteropoly anions and those of (PMo12O40)3-which were adapted from the literature, we discussed the influence of the central atoms on the electronic structures and catalytic properties of Keggin structure anions. The results show that the influences of the central atoms on electron cloud, electrostatic potential, total density of states are not clear. But the central atom can affect the components of the frontier orbitals HOMO and LUMO. The relative sequence of energy of LUMO and Fermi level is as follows: (AsMo12 -O40)3- > (PMo12O40)3- > (GeMo12O40)4- > (SiMo12O40)4-. The sequences of oxidation and catalytic activity are the same as the above. For (XMo12O40)n- (X = P, Si, Ge), Ot(terminal oxygen), Ob (bridge oxygen), Ox( central oxygen), Mo and X have the potential to participate in the catalytic reactions, whereas to (AsMo12O40)3- ,just As and Ob are exclusively active.
出处
《化学学报》
SCIE
CAS
CSCD
北大核心
1997年第4期356-362,共7页
Acta Chimica Sinica
基金
国家自然科学基金资助课题.
