Asymmetric Design of Spin-Crossover Complexes to Increase the Volatility for Surface Deposition

作者：Miguel Gakiya-Teruya, Xuanyuan Jiang, Duy Le, Ökten Üngör, Abdullah J. Durrani, John Koptur‐Palenchar, Jun Jiang, Tao Jiang, Mark W. Meisel, Hai‐Ping Cheng, Xiaoguang Zhang, Xiaoxiao Zhang, Talat S. Rahman, A. F. Hebard, Michael Shatruk · 发表于：Journal of the American Chemical Society · 年份：2021 · DOI：10.1021/jacs.1c04598 · 被引用次数：31 · 研究领域：Magnetism in coordination complexes、Magnetic properties of thin films、Molecular Junctions and Nanostructures

A mononuclear complex [Fe( t Bu 2 qsal) 2 ] has been obtained by a reaction between an Fe(II) precursor salt and a tridentate ligand 2,4-di( tert -butyl)-6-((quinoline-8-ylimino)methyl)phenol ( t Bu 2 qsalH) in the presence of triethylamine. The complex exhibits a hysteretic spin transition at 117 K upon cooling and 129 K upon warming, as well as light-induced excited spin-state trapping at lower temperatures. Although the strongly cooperative spin transition suggests substantial intermolecular interactions, the complex is readily sublimable, as evidenced by the growth of its single crystals by sublimation at 573 → 373 K and ∼10 –3 mbar. This seemingly antagonistic behavior is explained by the asymmetric coordination environment, in which the t Bu substituents and quinoline moieties appear on opposite sides of the complex. As a result, the structure is partitioned in well-defined layers separated by van der Waals interactions between the t Bu groups, while the efficient cooperative interactions within the layer are provided by the quinoline-based moieties. The abrupt spin transition is preserved in a 20 nm thin film prepared by sublimation, as evidenced by abrupt and hysteretic changes in the dielectric properties in the temperature range comparable to the one around which the spin transition is observed for the bulk material. The changes in the dielectric response are in excellent agreement with differences in the dielectric tensor of the low-spin and high-spin crystal struc...