六核钽铑二元混合簇合物的几何和电子结构

采用密度泛函理论对六核钽、铑八面体纯簇及其混合簇的几何结构和电子性质进行了研究.计算结果表明:大部分钽铑混合簇稳定构型的对称性均较低,为C1或Cs点群,只有Ta2Rh4Cl4H8(CN)6]4-团簇的稳定构型对称性较高,为C2h或C4v点群;混合簇的最高占据分子轨道(HOMO)与最低未占据分子轨道(LUMO)能隙(ΔEH-L)均较小,介于0.52-1.00eV之间;混合簇的前线轨道主要由骨架金属原子的d电子贡献,随着Rh原子替代Ta原子个数的递增,Ta—Rh键对混合簇稳定构型所起作用逐渐增加,Ta—Ta键所起作用减小,而Rh—Rh键为非键或反键性质.

Geometric and Electronic Structures of Hexanuclear Binary Ta/Rh Mixed Clusters

Density functional theory (DFT) was employed to investigate the geometric and electronic properties of a series of hexanuclear binary Ta/Rh clusters. The results show that most of the stable structures of the Ta/Rh mixed clusters have low symmetry and belong to the C₁ or C_s point groups while the Ta₂Rh₄Cl₄H₈(CN)₆]^4- clusters are highly symmetric (C_2h or C_4v). The energy gaps (△E_H-L) between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the mixed clusters are narrow and within 0.52-1.00 eV. A frontier orbital analysis of the mixed clusters clearly shows that the molecular orbitals are mainly composed of the d-orbitals of the skeleton metal atoms. When more rhodium atoms are substituted for tantalum atoms, the Ta-Rh bond has a greater influence on the stable structures of the mixed clusters and the influence of Ta-Ta bond decreases while the Rh-Rh bond has a non-bonding or anti-bonding nature.