Mikolasek Mirko, Manrique-Juarez Maria D, Shepherd Helena J, Ridier Karl, Rat Sylvain, Shalabaeva Victoria, Bas Alin-Ciprian, Collings Ines E, Mathieu Fabrice, Cacheux Jean, Leichle Thierry, Nicu Liviu, Nicolazzi William, Salmon Lionel, Molnár Gábor, Bousseksou Azzedine
ESRF-The European Synchrotron , 71 Avenue des Martyrs , 38000 Grenoble , France.
LCC-CNRS, Université de Toulouse, CNRS , 31077 Toulouse , France.
J Am Chem Soc. 2018 Jul 18;140(28):8970-8979. doi: 10.1021/jacs.8b05347. Epub 2018 Jul 3.
Molecular spin crossover complexes are promising candidates for mechanical actuation purposes. The relationships between their crystal structure and mechanical properties remain, however, not well understood. In this study, combining high pressure synchrotron X-ray diffraction, nuclear inelastic scattering, and micromechanical measurements, we assessed the effective macroscopic bulk modulus ( B = 11.5 ± 1.5 GPa), Young's modulus ( Y = 10.9 ± 1.0 GPa), and Poisson's ratio (ν = 0.34 ± 0.04) of the spin crossover complex [Fe(HB(tz))] (tz = 1,2,4-triazol-1-yl). Crystal structure analysis revealed a pronounced anisotropy of the lattice compressibility, which was correlated with the difference in spacing between the molecules as well as by the distribution of the stiffest C-H···N interactions in different crystallographic directions. Switching the molecules from the low spin to the high spin state leads to a remarkable drop of the Young's modulus to 7.1 ± 0.5 GPa both in bulk and thin film samples. The results highlight the application potential of these films in terms of strain (ε = -0.17 ± 0.05%), recoverable stress (σ = -21 ± 1 MPa), and work density ( W/V = 15 ± 6 mJ/cm).
分子自旋交叉配合物是用于机械驱动目的的有前途的候选材料。然而，它们的晶体结构与机械性能之间的关系仍未得到很好的理解。在本研究中，结合高压同步辐射X射线衍射、核非弹性散射和微机械测量，我们评估了自旋交叉配合物[Fe(HB(tz))]（tz = 1,2,4 - 三唑 - 1 - 基）的有效宏观体积模量（B = 11.5 ± 1.5 GPa）、杨氏模量（Y = 10.9 ± 1.0 GPa）和泊松比（ν = 0.34 ± 0.04）。晶体结构分析揭示了晶格压缩性的明显各向异性，这与分子间间距的差异以及不同晶体学方向上最硬的C - H···N相互作用的分布有关。将分子从低自旋态转变为高自旋态会导致块状和薄膜样品中的杨氏模量显著下降至7.1 ± 0.5 GPa。结果突出了这些薄膜在应变（ε = -0.17 ± 0.05%）、可恢复应力（σ = -21 ± 1 MPa）和功密度（W/V = 15 ± 6 mJ/cm）方面的应用潜力。
