Crystal packing energy calculations are applied to the [Fe(PM-L)₂(NCS)₂] family of spin crossover (SCO) complexes (PM-L = 4-substituted derivatives of the N-(2-pyridylmethylene)-4-aminobiphenyl ligand) with the aim of relating quantitatively the cooperativity of observed SCO transitions to intermolecular interactions in the crystal structures. This approach reveals a linear variation of the transition abruptness with the sum of the magnitudes of the interaction energy changes within the first molecular coordination sphere in the crystal structure. Abrupt transitions are associated with the presence of significant stabilising and destabilising changes in intermolecular interaction energies. While the numerical trend established for the PM-L family does not directly extend to other classes of SCO complex in which the intermolecular interactions may be very different, a plot of transition abruptness against the range of interaction energy changes normalised by the largest change shows a clustering of complexes with similar transition abruptness. The changes in intermolecular interactions are conveniently visualised using energy difference frameworks, which illustrate the cooperativity pathways of an SCO transition.

中文翻译：

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绘制自旋交叉复合物中的协同路径

晶体堆积能量计算应用于 [Fe(PM-L) ₂ (NCS) ₂ ] 自旋交叉 (SCO) 配合物家族 (PM-L = N的 4-取代衍生物-(2-吡啶基亚甲基)-4-氨基联苯配体)，目的是将观察到的 SCO 跃迁的协同性与晶体结构中的分子间相互作用定量相关。这种方法揭示了跃迁突变与晶体结构中第一个分子配位球内相互作用能量变化幅度之和的线性变化。突然转变与分子间相互作用能中存在显着的稳定和不稳定变化有关。虽然为 PM-L 家族建立的数值趋势并未直接扩展到其他类别的 SCO 复合物，其中分子间相互作用可能非常不同，跃迁突变与由最大变化归一化的相互作用能量变化范围的图显示了具有相似跃迁突变的复合物的聚集。使用能量差异框架可以方便地可视化分子间相互作用的变化，这说明了 SCO 跃迁的协同性途径。