Spectroscopic evidence for a unique bonding interaction in oxo-molybdenum dithiolate complexes:: Implications for σ electron transfer pathways in the pyranopterin dithiolate centers of enzymes
Spectroscopic evidence for a unique bonding interaction in oxo-molybdenum dithiolate complexes:: Implications for σ electron transfer pathways in the pyranopterin dithiolate centers of enzymes
复制标题
DOI：
10.1021/ic981126o
复制
发表时间：
1999-04-05
影响因子：
4.6
通讯作者：
Kirk, ML
中科院分区：
文献类型：
--
作者：
Inscore, FE;McNaughton, R;Kirk, ML
用溶液和固体电子吸收光谱、磁圆二色谱和共振拉曼光谱研究了LMoO（bdt）和LMoO（tdt）（L =三（3，5-二甲基-1-吡唑基）硼酸氢盐; bdt = 1，2-苯二硫醇盐; tdt = 3，4-甲苯二硫醇盐）的激发态电子结构。所观察到的能量，强度，和MCD带模式被发现是LMoO（S-S）化合物的特征，其中（S-S）是一个二硫代配体，形成一个五元螯合环与钼。对1，2-烯二硫纶配体片段-SC=CS-的从头计算表明，低能的S --> Mo电荷转移跃迁是由一组孤立的四个填充的二硫纶轨道的单电子促进引起的，这些轨道主要是硫的性质。共振拉曼激发配置文件已允许明确指定的ene-dithiolate正弦平面-->Mo d（xy）电荷转移跃迁。这是一个键到反键的转变，其强度直接探测硫共价对氧化还原轨道（Mo d（xy））的贡献。拉曼光谱已确定在362 cm（-1）（S-Mo-S弯曲）、393 cm（-1）（S-Mo-S伸缩）和932 cm（-1）（Mo=O伸缩）处的三个完全对称的振动模式，与在球形红细菌DMSO还原酶的共振拉曼光谱中观察到的大量低频模式形成对比。LMoO（S-S）复合物的这些结果被解释的上下文中的亚硫酸盐氧化酶的机制，由协调的ene-dithiolene（dithiolene）的还原电位的调制，和电子转移再生的吡喃蝶呤二硫纶钼酶活性位点的轨道途径。
Solution and solid state electronic absorption, magnetic circular dichroism, and resonance Raman spectroscopies have been used to probe in detail the excited state electronic structure of LMoO(bdt) and LMoO(tdt) (L = hydrotris(3,5-dimethyl-1-pyrazolyl)borate; bdt = 1,2-benzenedithiolate; tdt = 3,4-toluenedithiolate). The observed energies, intensities, and MCD band patterns are found to be characteristic of LMoO(S-S) compounds, where (S-S) is a dithiolate ligand which forms a five-membered chelate ring with Mo. Ab initio calculations on the 1,2-ene dithiolate ligand fragment, -SC=CS-, show that the low-energy S --> Mo charge transfer transitions result from one-electron promotions originating from an isolated set of four filled dithiolate orbitals that are primarily sulfur in character. Resonance Raman excitation profiles have allowed for the definitive assignment of the ene-dithiolate Sin-plane -->Mo d(xy) charge transfer transition. This is a bonding-to-antibonding transition, and its intensity directly probes sulfur covalency contributions to the redox orbital (Mo d(xy)). Raman spectroscopy has identified three totally symmetric vibrational modes at 362 cm(-1) (S-Mo-S bend), 393 cm(-1) (S-Mo-S stretch), and 932 cm(-1) (Mo=O stretch), in contrast to the large number low-frequency modes observed in the resonance Raman spectrum of Rhodobacter sphaeroides DMSO reductase. These results on LMoO(S-S) complexes are interpreted in the context of the mechanism of sulfite oxidase, the modulation of reduction potentials by a coordinated ene-dithiolate (dithiolene), and the orbital pathway for electron transfer regeneration of pyranopterin dithiolate Mo enzyme active sites.