Influence of a “Dangling” Co(II) Ion Bound to a [MnCo3O4] Oxo Cubane

Cobalt­(II),
in the presence of acetate and nitrate, quantitatively
adds to the manganese–cobalt oxido cubane MnIVCoIII3O4(OAc)5(py)3 (1) to furnish the pentametallic dangler complex MnIVCoIII3CoIIO4(OAc)6(NO3)­(py)3 (2). Complex 2 is structurally reminiscent of photosystem II’s oxygen-evolving
center, and is a rare example of a transition-metal “dangler”
complex. Superconducting quantum interference device magnetometry
and density functional theory calculations characterize 2 as having an S = 0 ground state arising from antiferromagnetic
coupling between the CoII and MnIV ions. At
higher temperatures, an uncoupled state dominates. The voltammogram
of 2 has four electrochemical events, two more than that
of its parent cubane 1, suggesting that addition of the
dangler increases available redox states. Structural, electrochemical,
and magnetic comparisons of complexes 1 and 2 allow a better understanding of the dangler’s influence on
a cubane.

在乙酸和硝酸盐的存在下，钴(II)可以定量地与锰-钴氧化立方烷MnIVCoIII3O4(OAc)5(py)3 (1)反应，生成五金属悬挂复合物MnIVCoIII3CoIIO4(OAc)6(NO3)­(py)3 (2)。复合物2的结构与光合系统II的氧释放中心相似，是过渡金属“悬挂”复合物的罕见实例。超导量子干涉仪磁性和密度泛函理论计算表明，复合物2具有由CoII和MnIV离子之间的反铁磁耦合产生的S = 0基态。在较高温度下，解耦状态占主导地位。复合物2的伏安图中存在四个电化学事件，比其母体立方烷1多两个，这表明悬挂基团的加入增加了可用的氧化还原状态。通过对比复合物1和2的结构、电化学和磁性特征，可以更深入地理解悬挂基团对立方烷的影响。