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采用密度泛函理论方法,在TZ2P-STO基组水平下,对金属四重键化合物M2Cl4(PMe3)4(M=Cr,Mo,W)和Mo2X4(PMe3)4(X=F,Cl,Br,I)的几何结构进行优化,分析了电子结构,并运用TDDFT方法对其低占据激发态进行了计算.考虑相对论效应的ZORA方法能够较好地重现M2X4(PMe3)4的几何结构.M2X4(PMe3)4的电子结构分析表明其d电子的组态为σ2π4δ2,前线轨道能级顺序为πlig<πd/σd<δd<δd*.金属原子和卤素配体的改变虽然使轨道能量发生变化,但没有影响轨道的排布顺序.TDDFT方法对M2X4(PMe3)4δd→δd*和πd→δd*跃迁能量的计算较为准确,对πlig→δd*(LMCT)跃迁能量的计算误差较大.金属原子、卤素配体以及相对论效应对激发能的影响可以根据分子轨道能级的变化给予解释.
The density functional theory (DFT) method was used to investigate the thermal stability of the metal quadruplex compounds M2Cl4 (PMe3) 4 (M = Cr, Mo, W) and Mo2X4 (PMe3) 4 (X = F, Cl, Br , I), the electronic structure was analyzed, and the TDDFT method was used to calculate the low-occupied excited states. The ZORA method considering the relativistic effect can well reproduce the geometry of M2X4 (PMe3) 4. (PMe3) 4 shows that its d-electron configuration is σ2π4δ2 and its frontier orbital order is πlig <πd / σd <δd <δd *. Although the changes of metal atoms and halogen ligands change the orbital energies, But does not affect the order of orbital arrangement.DDFT method is more accurate for calculating the energies of 4δd → δd * and πd → δd * transitions of M2X4 (PMe3), and large errors for the energy of πlig → δd * (LMCT) The effects of halogen ligands and relativistic effects on the excitation energy can be explained by the changes in molecular orbital energy levels.