Departament de Química Inorgànica i Orgànica and Institut de Recerca de Química Teòrica i Computacional, Universitat de Barcelona, Diagonal 645, 08028 Barcelona, Spain.
Departament de Ciència de Materials i Química Física and Institut de Recerca de Química Teòrica i Computacional, Universitat de Barcelona, Diagonal 645, 08028 Barcelona, Spain.
Phys Chem Chem Phys. 2023 May 3;25(17):12490-12499. doi: 10.1039/d3cp00250k.
Exploring the chemical space of a given ligand aiming to modulate its ligand field strength is a versatile strategy for the fine-tuning of physical properties such as the transition temperature () of spin-crossover (SCO) complexes. The computational study presented herein aims at systematically exploring the extent to which the ligand substituent effects can modulate in two families of Fe(III) SCO systems with a NO coordination environment and at identifying the best descriptors for fast and accurate prediction of changes in upon ligand functionalization. B3LYP* calculations show that the attachment of substituents to β-ketoiminato fragments (L) leads to drastic changes in , while functionalization of phenolato moieties (L) allows for a finer degree of control over . Natural Bond Orbital (NBO) charges of the donor atoms, Hammett parameters for both and -functionalization of L, and Swain-Lupton parameters for L and -functionalization of L have been found to be the suitable descriptors for predicting the changes in . Further analysis of the ligand-field splitting in such systems rationalizes the observed trends and shows that ligand substituents modify both the σ and π bonds between the Fe(III) center and the ligands. Thus, we provide simple yet reliable guidelines for the rational design of new SCO systems with specific values of based on their ligand design.
探索给定配体的化学空间，旨在调节其配体场强度，是微调物理性质（如自旋交叉（SCO）配合物的转变温度（））的一种通用策略。本文提出的计算研究旨在系统地探索配体取代基效应在具有 NO 配位环境的两种 Fe(III) SCO 体系中调节的程度，以及确定最佳描述符，以快速准确地预测配体功能化后 的变化。B3LYP*计算表明，β-酮亚胺片段（L）上取代基的附加导致显著变化，而酚基部分（L）的功能化允许对 进行更精细的控制。已发现供体原子的自然键轨道（NBO）电荷、L 的和 -功能化的 Hammett 参数以及 L 和 -功能化的 L 的 Swain-Lupton 参数是预测变化的合适描述符。对这些体系中配体场分裂的进一步分析合理化了观察到的趋势，并表明配体取代基修饰了 Fe(III)中心与配体之间的 σ 和 π 键。因此，我们为基于配体设计的具有特定 值的新型 SCO 系统的合理设计提供了简单但可靠的指导方针。
