Spikes Geoffrey H, Sproules Stephen, Bill Eckhard, Weyhermüller Thomas, Wieghardt Karl
Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany.
Inorg Chem. 2008 Dec 1;47(23):10935-44. doi: 10.1021/ic801122m.
The electronic structures of chromium and vanadium centers coordinated by three reduced 1,2-diketones have been elucidated by using density functional theory (DFT) calculations and a host of physical methods: X-ray crystallography; cyclic voltammetry; ultraviolet-visible (UV-vis), nuclear magnetic resonance (NMR), and electron paramagnetic resonance (EPR) spectroscopy; and magnetic susceptibility measurements. The metal center in octahedral [CrIII(L*)3]0 (1), a CrIII (d3) ion is coupled antiferromagnetically to three monoanionic ligand pi-radicals affording an S ) 0 ground state. In contrast, Na2(Et2O)2[VIV(LRed)3] (2) (S ) 1/2), possesses a central VIV (d1) ion O,OE-coordinated to three closed-shell, doubly reduced ligands which in turn are coordinated by two Na cations enforcing a trigonal prismatic geometry at the vanadium center. 2 can be oxidized electrochemically by one and two electrons generating a monoanion, [V(L)3]1-, and a neutral species, [V(L)3]0, respectively. DFT calculations atthe B3LYP level show that the one-electron oxidized product contains an octahedral VIV ion coupled antiferromagnetically to one monoanionic ligand pi-radical [VIV(L*)(LRed)2]1- (S ) 0). In contrast, the two-electron oxidized product contains a VIII ion coupled antiferromagnetically to three ligand pi-radicals in an octahedral field[VIII(L*)3]0 (S ) 1/2).
通过使用密度泛函理论（DFT）计算以及一系列物理方法，阐明了由三个还原的1,2 - 二酮配位的铬和钒中心的电子结构：X射线晶体学；循环伏安法；紫外 - 可见（UV - vis）、核磁共振（NMR）和电子顺磁共振（EPR）光谱；以及磁化率测量。八面体[CrIII(L*)3]0（1）中的金属中心，一个CrIII（d3）离子与三个单阴离子配体π - 自由基反铁磁耦合，提供了一个S = 0的基态。相比之下，Na2(Et2O)2[VIV(LRed)3]（2）（S = 1/2），具有一个中心VIV（d1）离子，通过O，O配位与三个闭壳层、双还原的配体相连，这些配体又由两个Na阳离子配位，在钒中心强制形成三角棱柱几何结构。2可以分别通过一个和两个电子进行电化学氧化，生成单阴离子[V(L)3]1 - 和中性物种[V(L)3]0。在B3LYP水平的DFT计算表明，单电子氧化产物包含一个八面体VIV离子，与一个单阴离子配体π - 自由基[VIV(L*)(LRed)2]1 - 反铁磁耦合（S = 0）。相比之下，双电子氧化产物包含一个VIII离子，在八面体场中与三个配体π - 自由基反铁磁耦合[VIII(L*)3]0（S = 1/2）。
