Maniaki Diamantoula, Pilichos Evangelos, Perlepes Spyros P
Department of Chemistry, University of Patras, Patras, Greece.
Front Chem. 2018 Oct 9;6:461. doi: 10.3389/fchem.2018.00461. eCollection 2018.
The area of 3d-metal coordination clusters that behave as Single-Molecule Magnets (SMMs) is now quite mature within the interdisciplinary field of Molecular Magnetism. This area has created a renaissance in Inorganic Chemistry. From the synthetic Inorganic Chemistry viewpoint, the early years of "try and see" exercises (1993-2000) have been followed by the development of strategies and strict approaches. Our review will first summarize the early synthetic efforts and routes for the preparation of polynuclear 3d-metal SMMs, and it will be then concentrated on the description of the existing strategies. The former involve the combination of appropriate 3d-metal-containing starting materials (simple salts with inorganic anions, metal cardoxylates, and pre-formed carboxylate clusters, metal phosphonates) and one or two primary organic ligands; the importance of the end-on azido group as a ferromagnetic coupler in 3d-metal SMM chemistry will be discussed. The utility of comproportionation reactions and the reductive aggregation route for the construction of manganese SMMs will also be described. Most of the existing strategies for the synthesis of SMMs concern manganese. These involve substitution of carboxylate ligands in pre-formed SMMs by other carboxylate or non-carboxylate groups, reduction procedures for the { } SMMs, spin "tweaking," "switching on" SMM properties upon conversion of low-spin clusters into high-spin ones, ground-state spin switching and enhancing SMM properties via targeted structural distortions, the use of radical bridging ligands and supramolecular approaches. A very useful strategy is also the "switching on" of SMM behavior through replacement of bridging hydroxide groups by end-on azido or isocyanato ligands in clusters. Selected examples will be mentioned and critically discussed. Particular emphasis will be given on the criteria for the choice of ligands.
在分子磁学这一跨学科领域中，表现为单分子磁体（SMMs）的三维金属配位簇领域如今已相当成熟。该领域在无机化学领域引发了一场复兴。从合成无机化学的角度来看，早期的“尝试与观察”阶段（1993 - 2000年）之后，相继发展出了各种策略和严谨的方法。我们的综述将首先总结早期合成多核三维金属单分子磁体的努力和路线，然后将集中描述现有的策略。前者涉及合适的含三维金属起始材料（含无机阴离子的简单盐、金属羧酸盐、预先形成的羧酸盐簇、金属膦酸盐）与一种或两种主要有机配体的组合；将讨论端基叠氮基团作为三维金属单分子磁体化学中铁磁耦合剂的重要性。还将描述歧化反应和还原聚集路线在构建锰单分子磁体中的应用。现有的大多数单分子磁体合成策略都与锰有关。这些策略包括用其他羧酸盐或非羧酸盐基团取代预先形成的单分子磁体中的羧酸盐配体、{ }单分子磁体的还原程序、自旋“微调”、将低自旋簇转化为高自旋簇时“开启”单分子磁体性质、基态自旋切换以及通过有针对性的结构畸变增强单分子磁体性质、使用自由基桥连配体和超分子方法。通过用端基叠氮或异氰酸酯配体取代簇中的桥连羟基基团来“开启”单分子磁体行为也是一种非常有用的策略。将提及并批判性地讨论一些选定的例子。将特别强调配体选择的标准。
