Magnetism and variable temperature and pressure crystal structures of a linear oligonuclear cobalt bis-semiquinonate.
Magnetism and variable temperature and pressure crystal structures of a linear oligonuclear cobalt bis-semiquinonate.
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DOI：
10.1039/c6dt02024k
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发表时间：
2016-08
影响因子：
4
通讯作者：
J. Overgaard;L. Møller;M. A. Borup;M. Tricoire;J. P. Walsh;M. Diehl;E. Rentschler
中科院分区：
文献类型：
--
作者：
J. Overgaard;L. Møller;M. A. Borup;M. Tricoire;J. P. Walsh;M. Diehl;E. Rentschler
第一种低聚钴二氧戊环配合物Co_3（3，5-DBSQ）_2（（t）BuCOO）_4（NEt_3）_2，1（其中DBSQ为3，5-二叔丁基半醌）在20 ~ 200 K温度范围内的晶体结构进行了研究。尽管钴-二氧杂环戊烯配合物通常被称为其广泛的能力，表现出价互变异构（VT），我们在这里表明，化合物1的分子几何形状基本上是不变的，在整个温度范围内，表明完全没有电子转移配体和金属之间。磁化率测量清楚地支持缺乏VT之间的8和300 K。晶体结构也确定在升高的压力范围从0到2.5 GPa。令人惊讶的是，晶体结构的响应取决于加压的动力学：快速加压到2 GPa后，发生结构相变;然而，当压力递增到2.6 GPa时，这是不存在的。在新的高压相，Z'为2，其中一个分子的配位从μ2：κO：κO'变为μ2：κ（2）O，O '：κ O'，而另一个分子保持不变。尽管分子连接性发生了显著变化，但晶体结构的分析表明，相变使分子的自旋和氧化态保持不变。在高压晶体结构中的分子间相互作用已经用赫希菲尔德表面进行了分析，但它们不能解释相变的起源。在该第一低聚Co-二氧杂环戊烯络合物中缺乏VT被推测是由于末端Co原子的配位几何结构，其是三角形双配位的，不同于更常见的八面体配位。通过Oh的hs-to-ls变化获得的能量等于Δ，而在三角双锥（C3 v）的情况下，能量增益等于d（z（2））和简并d（x（2）- y（2））/d（xy）之间的分裂，其显著更小。
The crystal structure of the first oligomeric cobalt dioxolene complex, Co3(3,5-DBSQ)2((t)BuCOO)4(NEt3)2, 1, where DBSQ is 3,5-di-tert-butyl-semiquinonate, has been studied at various temperatures between 20 and 200 K. Despite cobalt-dioxolene complexes being generally known for their extensive ability to exhibit valence tautomerism (VT), we show here that the molecular geometry of compound 1 is essentially unchanged over the full temperature range, indicating the complete absence of electron transfer between ligand and metal. Magnetic susceptibility measurements clearly support the lack of VT between 8 and 300 K. The crystal structure is also determined at elevated pressures in the range from 0 to 2.5 GPa. The response of the crystal structure is surprisingly dependent on the dynamics of pressurisation: following rapid pressurization to 2 GPa, a structural phase transition occurs; yet, this is absent when the pressure is increased incrementally to 2.6 GPa. In the new high pressure phase, Z' is 2 and one of the two molecules displays changes in the coordination of one bridging carboxylate from μ2:κO:κO' to μ2:κ(2)O,O':κO', while the other molecule remains unchanged. Despite the significant changes to the molecular connectivity, analysis of the crystal structures shows that the phase transition leaves the spin and oxidation states of the molecules unaltered. Intermolecular interactions in the high pressure crystal structures have been analysed using Hirshfeld surfaces but they cannot explain the origin of the phase transition. The lack of VT in this first oligomeric Co-dioxolene complex is speculated to be due to the coordination geometry of the terminal Co-atoms, which are trigonal bipyramidally coordinated, different from the more common octahedral coordination. The energy that is gained by a hs-to-ls change in Oh is equal to Δ, while in the case of the trigonal bipyramidal (C3v), the energy gain is equal to the splitting between d(z(2)) and degenerate d(x(2) - y(2))/d(xy), which is significantly less.