分子复合物 [Fe(H2B(pz)2)2(phen)] 中耦合结构和自旋态跃迁的压力调节,Inorganic Chemistry

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分子复合物 [Fe(H2B(pz)2)2(phen)] 中耦合结构和自旋态跃迁的压力调节
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2022-09-26 , DOI: 10.1021/acs.inorgchem.2c02286
Damian Paliwoda ₁ , Laure Vendier ₁ , William Nicolazzi ₁ , Gábor Molnár ₁ , Azzedine Bousseksou ₁

Affiliation

在一些过渡金属配合物中伴随着分子自旋交叉（SCO）现象的大体积变化经常促使SCO与其他不稳定性耦合。了解这种耦合相变的驱动机制不仅出于基本原因很重要，而且为多功能材料的开发提供了空间。一般的理论期望是耦合具有弹性起源，并且可以通过外部施加的压力来调整转变的顺序，但专门的实验仍然很少。在这里，我们使用高压和低温单晶 X 射线衍射来研究分子配合物 [Fe ^II (H ₂ B(pz) ₂) ₂ (bipy)] 和 [Fe ^II (H ₂ B(pz) ₂ ) ₂ (phen)]。在联吡啶配合物中，SCO 在整个T、P范围（100-300 K，0-2 GPa）上是连续的和同构的。然而，在菲咯啉衍生物中，SCO 伴随着对称破缺转变（C 2/ c到P 1̅）。结构分析表明，这两种现象之间的耦合可以通过外部压力来调节，从几乎同时的 HS _{C 2/ c} –LS _P 1̅ 转变为 HS _{C 2/ c序列}–LS _{C 2/ c} –LS _P 1̅ 跃迁。自发应变和有序参数行为的相关性突出表明，“分离”的转变仍然通过应变耦合保持连接，而“同时”的转变是部分分裂的。

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Pressure Tuning of Coupled Structural and Spin State Transitions in the Molecular Complex [Fe(H2B(pz)2)2(phen)]

The large volume change, which accompanies the molecular spin crossover (SCO) phenomenon in some transition metal complexes, prompts frequently the coupling of the SCO with other instabilities. Understanding the driving mechanism(s) of such coupled phase transitions is not only important for fundamental reasons but also provides scope for the development of multifunctional materials. The general theoretical expectation is that the coupling has elastic origin, and the sequence of transitions can be tuned by an externally applied pressure, but dedicated experiments remain scarce. Here, we used high-pressure and low-temperature single-crystal X-ray diffraction to investigate the high-spin (HS) to low-spin (LS) transitions in the molecular complexes [Fe^II(H₂B(pz)₂)₂(bipy)] and [Fe^II(H₂B(pz)₂)₂(phen)]. In the bipyridine complex, the SCO is continuous and isostructural over the whole T, P-range (100–300 K, 0–2 GPa). In the phenanthroline derivative, however, the SCO is concomitant with a symmetry-breaking transition (C2/c to P1̅). Structural analysis reveals that the coupling between the two phenomena can be tuned by external pressure from a virtually simultaneous HS_C2/c–LS_P1̅ transition to the sequence of HS_C2/c–LS_C2/c–LS_P1̅ transitions. The correlation of spontaneous strain and order parameter behaviors highlights that the “separated” transitions remain still connected via strain coupling, whereas the “simultaneous” transitions are partially split.

更新日期：2022-09-26

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