Elastic Frustration Triggering Photoinduced Hidden Hysteresis and Multistability in a Two-Dimensional Photoswitchable Hofmann-Like Spin-Crossover Metal–Organic Framework

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 firs...

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Veröffentlicht in:Inorganic chemistry 2016-11, Vol.55 (22), p.11652-11661
Hauptverfasser: Milin, Eric, Patinec, Véronique, Triki, Smail, Bendeif, El-Eulmi, Pillet, Sébastien, Marchivie, Mathieu, Chastanet, Guillaume, Boukheddaden, Kamel
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Sprache:eng
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Zusammenfassung: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.
ISSN:0020-1669
1520-510X
DOI:10.1021/acs.inorgchem.6b01081