簇合物Mo_2X_8~(4-)(X=Cl,Br)低能态电子光谱

应用间略微分重叠自洽场和组态作用(INDO/S-CI)方法,计算双核簇合物Mo_2X_8~(4-)(X=Cl,Br)基态~1A_(1g)至不同低能态的d电子自旋允许的跃迁能,得出Mo—Mo四重键均裂时所需的能量大小依次为键σ>π>>δ。对于Mo_2Cl_8~(4-)簇合物态~1A_(1g)→1~1A_(2u)(δ→δ~*)和~1A_(1g)→2~1E_g(π→δ~*)的电子跃迁能,理论值(15584和22587cm~(-1))与低温时测得光谱实验值(18083和22000cm~(-1))较为接近。此外,本文还提出了簇合物Mo_2X_8~(4-)的态相同而X不同时,电子跃迁能变化,主要决定于参与电子转移过程的分子轨道组成成份的看法。

Electronic Spectrum on Low-Lying States of Binuclear Transition Metal Cluster Mo_2x_8~(4-)(X=Cl,Br)

The method of self-consistent field of the intermediate neglect of differential overlap followed by a modest configuration interation(INDO/S-CI) has been used in the calculateion of the electronic excited energies on the low-lying states of binuclear transition metal clusters Mo2X84- (X = Cl,Br), which are spin allowed excitation of d-electron from ground state 1A1g. It is found that the variances of the cleavaged energy on the multiple bond of Mo-Mo decrease as the sequence of typical bond σ>π>>δ due to the absorption of one photo by ground state in the Mo2X84- clusters , according to the excited energies from bur calculation results. It is shown that the calculated wavenumbers(15584, 22587cm-1) of the absorption bonds are in agreement well with the observed ones(18083,22000cm-1) from the election excitations of the state 1A1g-11A2u(δ→δ*)and seperately in the Mo2X84- cluster. It points out that the variances of elec-tronic excited energy between the different X atoms at the same excited state in the Mo2X84- clusters depend mostly on the components of the participant molecular orbitals during electron transfer processes.