Complete set of elastic moduli of a spin-crossover solid: Spin-state dependence and mechanical actuation

Abstract : Mol. spin crossover complexes are promising candidates for mech. actuation purposes. The relationships between their crystal structure and mech. properties remain, however, not well understood. In this study, combining high pressure synchrotron X-ray diffraction, nuclear inelastic scattering, and micromech. 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 [FeII(HB(tz)3)2] (tz = 1,2,4-triazol-1-yl). Crystal structure anal. revealed a pronounced anisotropy of the lattice compressibility, which was correlated with the difference in spacing between the mols. as well as by the distribution of the stiffest C-H···N interactions in different crystallog. directions. Switching the mols. 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 d. (W/V = 15 ± 6 mJ/cm3).
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Submitted on : Thursday, December 20, 2018 - 10:58:16 AM
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Mirko Mikolasek, Maria D. Manrique-Juarez, H. J. Shepherd, Karl Ridier, Sylvain Rat, et al.. Complete set of elastic moduli of a spin-crossover solid: Spin-state dependence and mechanical actuation. Journal of the American Chemical Society, American Chemical Society, 2018, 140 (28), pp.8970-8979. ⟨10.1021/jacs.8b05347⟩. ⟨hal-01961781⟩

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