title: 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 FeIIsites. 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 FeIIsites. 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.
authors.affiliation: Chimie, Electrochimie Moléculaires, Chimie Analytique, Université de Bretagne Occidentale, UMR CNRS 6521 , 6 Avenue Victor Le Gorgeu, CS 93837, 29285 Brest Cedex 3, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Milin
authors.affiliation: Chimie, Electrochimie Moléculaires, Chimie Analytique, Université de Bretagne Occidentale, UMR CNRS 6521 , 6 Avenue Victor Le Gorgeu, CS 93837, 29285 Brest Cedex 3, France.
authors.forename: Véronique
authors.initials: V
authors.lastname: Patinec
authors.affiliation: Chimie, Electrochimie Moléculaires, Chimie Analytique, Université de Bretagne Occidentale, UMR CNRS 6521 , 6 Avenue Victor Le Gorgeu, CS 93837, 29285 Brest Cedex 3, France.
authors.forename: Smail
authors.initials: S
authors.lastname: Triki
authors.affiliation: Institut Jean Barriol, Université de Lorraine, CRM2, UMR CNRS 7036 , B.P. 70239, F-54506 Vandoeuvre-lès-Nancy, France.
authors.forename: El-Eulmi
authors.initials: EE
authors.lastname: Bendeif
authors.affiliation: Institut Jean Barriol, Université de Lorraine, CRM2, UMR CNRS 7036 , B.P. 70239, F-54506 Vandoeuvre-lès-Nancy, France.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Pillet
authors.affiliation: Institut de Chimie de la Matière Condensée de Bordeaux, Université de Bordeaux , 87 Av. Doc. A. Schweitzer, F-33608 Pessac, France.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Marchivie
authors.affiliation: Institut de Chimie de la Matière Condensée de Bordeaux, Université de Bordeaux , 87 Av. Doc. A. Schweitzer, F-33608 Pessac, France.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Chastanet
authors.affiliation: GEMaC, Université Paris-Saclay, CNRS, Université de Versailles Saint-Quentin-en-Yvelines , 45 Avenue des Etats-Unis, 78035 Versailles Cedex, France.
authors.forename: Kamel
authors.initials: K
authors.lastname: Boukheddaden