Missana Andrea, Hauser Andreas, Lawson Daku Latévi Max
Université de Genève, 30 quai Ernest-Ansermet, CH-1211Genève 4, Switzerland.
J Phys Chem A. 2022 Sep 15;126(36):6221-6235. doi: 10.1021/acs.jpca.2c05070. Epub 2022 Sep 6.
Using the supramolecular approach developed for the study of the guest-host interactions in the zeolite Y encapsulated [Fe(bpy)] compound: [Fe(bpy)]@Y (bpy = 2,2'-bipyridine) [Vargas et al., 2009, 5, 97-115], we apply density functional theory (DFT) to the study of the influence of zeolite Y encapsulation on the structural and energetic properties of [Co(bpy)] in the low-spin (LS) and high-spin (HS) states, while revisiting [Fe(bpy)]@Y. Although the accurate prediction of the HS-LS energy difference Δ remains challenging for current DFT methods, they give accurate estimates of its variation Δ(Δ) in a series of complexes of a given transition metal ion. Therefore, denoting [M(bpy)]@Y as the supramolecular model of the inclusion compounds, the values of Δ for the bpy complexes in the gas phase and in the supercage of zeolite Y were determined by combining the DFT estimates of Δ(Δ) in the series {[M(NCH)], [M(bpy)], and [M(bpy)]@Y}, with accurate CCSD(T) estimates of Δ in the benchmark complexes [M(NCH)] (M = Fe, Co) [Lawson Daku et al., , 2012, 8, 4216-4231]. Generalized gradient approximations as well as global and range-separated hybrids were employed. In order to better account for the key role of dispersion, they were also augmented with the semiempirical D2, D3BJ, and D3BJM dispersion corrections when available. The use of the D3BJ and D3BJM corrections led to similar results, and this is only with the use of the D2 scheme that (i) the free and encapsulated [Fe(bpy)] are correctly predicted as LS species and that (ii) the encapsulation of both complexes translates into a destabilization of their HS state with respect to their LS state. The increase of the HS-LS energy difference is smaller for [Co(bpy)] than [Fe(bpy)] because the HS-LS molecular volume difference Δ in [Co(bpy)] is ∼50% smaller than in [Fe(bpy)]. Periodic DFT calculations performed on crystalline [M(bpy)]@Y show that the employed [M(bpy)]@Y supramolecular model allows the influence of encapsulation on the geometry and the spin-state energetics of [M(bpy)] (M = Fe, Co) to be quantitatively captured.
利用为研究封装在Y型沸石中的[Fe(bpy)]化合物（[Fe(bpy)]@Y，bpy = 2,2'-联吡啶）[瓦尔加斯等人，2009年，第5卷，97 - 115页]中的客体-主体相互作用而开发的超分子方法，我们应用密度泛函理论（DFT）来研究Y型沸石封装对处于低自旋（LS）和高自旋（HS）态的[Co(bpy)]的结构和能量性质的影响，同时重新审视[Fe(bpy)]@Y。尽管对于当前的DFT方法而言，准确预测HS - LS能量差Δ仍然具有挑战性，但它们能准确估计给定过渡金属离子的一系列配合物中其变化量Δ(Δ)。因此，将[M(bpy)]@Y视为包合物的超分子模型，通过结合系列{[M(NCH)]、[M(bpy)]和[M(bpy)]@Y}中Δ(Δ)的DFT估计值与基准配合物[M(NCH)]（M = Fe、Co）[劳森·达库等人，2012年，第8卷，4216 - 4231页]中Δ的精确CCSD(T)估计值，确定了气相和Y型沸石超笼中bpy配合物的Δ值。采用了广义梯度近似以及全局和范围分离的杂化函数。为了更好地考虑色散的关键作用，在可用时还使用了半经验的D2、D3BJ和D3BJM色散校正。使用D3BJ和D3BJM校正得到了相似的结果，只有使用D2方案时，才能（i）正确预测自由态和封装态的[Fe(bpy)]为LS物种，以及（ii）两种配合物的封装都导致其HS态相对于LS态不稳定。[Co(bpy)]的HS - LS能量差的增加比[Fe(bpy)]小，因为[Co(bpy)]中HS - LS分子体积差Δ比[Fe(bpy)]小约50%。对晶体[M(bpy)]@Y进行的周期性DFT计算表明，所采用的[M(bpy)]@Y超分子模型能够定量捕捉封装对[M(bpy)]（M = Fe、Co）的几何结构和自旋态能量学的影响。
