Institut de Physique et Chimie des Matériaux (IPCMS), Université de Strasbourg, F-67034, Strasbourg, France.
Swiss Light Source, Paul Scherrer Institut (PSI), CH-5232, Villigen, Switzerland.
Adv Mater. 2018 Mar;30(11). doi: 10.1002/adma.201705416. Epub 2018 Jan 22.
The realization of spin-crossover (SCO)-based applications requires study of the spin-state switching characteristics of SCO complex molecules within nanostructured environments, especially on surfaces. Except for a very few cases, the SCO of a surface-bound thin molecular film is either quenched or heavily altered due to: (i) molecule-surface interactions and (ii) differing intermolecular interactions in films relative to the bulk. By fabricating SCO complexes on a weakly interacting surface, the interfacial quenching problem is tackled. However, engineering intermolecular interactions in thin SCO active films is rather difficult. Here, a molecular self-assembly strategy is proposed to fabricate thin spin-switchable surface-bound films with programmable intermolecular interactions. Molecular engineering of the parent complex system [Fe(H B(pz) ) (bpy)] (pz = pyrazole, bpy = 2,2'-bipyridine) with a dodecyl (C ) alkyl chain yields a classical amphiphile-like functional and vacuum-sublimable charge-neutral Fe complex, [Fe(H B(pz) ) (C -bpy)] (C -bpy = dodecyl[2,2'-bipyridine]-5-carboxylate). Both the bulk powder and 10 nm thin films sublimed onto either quartz glass or SiO surfaces of the complex show comparable spin-state switching characteristics mediated by similar lamellar bilayer like self-assembly/molecular interactions. This unprecedented observation augurs well for the development of SCO-based applications, especially in molecular spintronics.
实现基于自旋交叉（SCO）的应用需要研究 SCO 配合物分子在纳米结构环境中，特别是在表面上的自旋态转换特性。除了极少数情况外，由于以下两个原因，表面结合的薄分子膜的 SCO 要么被猝灭，要么发生重大改变：（i）分子-表面相互作用和（ii）与体相相比，薄膜中分子间相互作用的差异。通过在弱相互作用表面上制造 SCO 配合物，可以解决界面猝灭问题。然而，在薄的 SCO 活性薄膜中工程化分子间相互作用是相当困难的。在这里，提出了一种分子自组装策略，以制造具有可编程分子间相互作用的可旋转表面结合的薄膜。母体配合物系统[Fe(H B(pz) )(bpy)]（pz=吡唑，bpy=2,2'-联吡啶）的分子工程设计，具有十二烷基（C ）烷基链，得到了一种经典的两亲性类似功能和真空升华的电荷中性 Fe 配合物，[Fe(H B(pz) )(C -bpy)]（C -bpy=十二烷基[2,2'-联吡啶]-5-羧酸酯）。无论是大块粉末还是蒸发到石英玻璃或 SiO 表面的 10nm 厚薄膜，都表现出相似的自旋态转换特性，这是由类似的层状双层自组装/分子相互作用介导的。这种前所未有的观察结果为基于 SCO 的应用的发展，特别是在分子自旋电子学中，带来了良好的前景。
