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Elastic frustration triggering photoinduced hidden hysteresis and multistability in a two-dimensional photoswitchable Hofmann-like spin-Crossover metal–organic framework

Abstract : We report a two-dimensional Hofmann-like spin-crossover (SCO) material, [Fe(trz-py)2{Pt(CN)4}]·3H2O, built from [FePt(CN)4] layers separated by interdigitated 4-(2-pyridyl)-1,2,4,4H-triazole (trz-py) ligands with two symmetrically inequivalent FeII sites. This compound exhibits an incomplete first-order spin transition at 153 K between fully high-spin (HS-HS) and intermediate high-spin low-spin (HS-LS) ordered states. At low temperature, it undergoes a bidirectional photoswitching to HS-HS and fully low-spin (LS-LS) states with green and near-IR light irradiation, respectively, with associated T(LIESST = Light-Induced Excited Spin-State Trapping) and T(reverse-LIESST) values of 52 and 85 K, respectively. Photomagnetic investigations show that the reverse-LIESST process, performed from either HS-HS or HS-LS states, enables access to a hidden stable LS-LS state, revealing the existence of a hidden thermal hysteresis. Crystallographic investigations allowed to identify that the strong metastability of the HS-LS state originates from the existence of a strong elastic frustration causing antiferroelastic interactions within the [FePt(CN)4] layers, through the rigid NC-Pt-CN bridges connecting the inequivalent FeII sites. The existence of the stable LS-LS state paves the way for a multidirectional photoswitching and allows potential applications for electronic devices based on ternary digits.
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https://hal.archives-ouvertes.fr/hal-01407977
Contributor : Stéphane Toulin <>
Submitted on : Friday, December 2, 2016 - 6:43:11 PM
Last modification on : Wednesday, July 15, 2020 - 10:30:02 AM

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Eric Milin, Véronique Patinec, Smail Triki, El-Eulmi Bendeif, Sébastien Pillet, et al.. Elastic frustration triggering photoinduced hidden hysteresis and multistability in a two-dimensional photoswitchable Hofmann-like spin-Crossover metal–organic framework. Inorganic Chemistry, American Chemical Society, 2016, 55 (22), pp.11652-11661. ⟨10.1021/acs.inorgchem.6b01081⟩. ⟨hal-01407977⟩

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