Metal−organic frameworks (MOFs) provide versatile platforms to construct multi-responsive materials. Herein, by introducing the neutral tetradentate ligand and the linear dicyanoaurate(I) anion, we reported a rare cationic MOF [Fe II (TPB){Au I (CN) 2 }]I•4H 2 O•4DMF (TPB = 1,2,4,5-tetra(pyridin-4-yl)benzene) with hysteretic spin-crossover (SCO) behavior near room temperature. This hybrid framework with an open metal site (Au I ) exhibits redox-programmable capability toward dihalogen molecules. By means of post-synthetic modification, all the linear [Au I (CN) 2 ] − linkers can be oxidized to square planar [Au III (CN) 2 X 2 ] − units, which results in the hysteretic SCO behaviors switching from one-step to two-step for Br 2 and threestep for I 2 . More importantly, the stepwise SCO behaviors can go back to one-step via the reduction by L-ascorbic acid (AA). Periodic DFT calculations using various SCAN-type exchange-correlation functionals have been employed to rationalize the experimental data. Hence, these results demonstrate for the first time that switchable one-/two-/three-stepped SCO dynamics can be manipulated by chemical redox reactions, which opens a new perspective for multi-responsive molecular switches.
Introducing magnetic switchability into artificial molecular machines is fascinating for precise control of magnetism via external stimuli. Herein, a field‐induced CoII single‐molecule magnet was found to exhibit the reversible switch of Jahn–Teller distortion near room temperature, along with thermal conformational motion of the 18‐crown‐6 rotor, which pulls the coordinated H2O to rotate through intermolecular hydrogen bonds and triggers a single‐crystal‐to‐single‐crystal phase transition with Twarm=282 K and Tcool=276 K. Interestingly, the molecular magnetic anisotropy probed by single‐crystal angular‐resolved magnetometry revealed the reorientation of easy axis by 14.6°. Moreover, ON/OFF negative magnetodielectric effects were respectively observed in the high‐/low‐temperature phase, which manifests the spin‐lattice interaction in the high‐temperature phase could be stronger, in accompanied by the hydrogen bonding between the rotating 18‐crown‐6 and the coordinated H2O.
Introducing magnetic switchability into artificial molecular machines is fascinating for precise control of magnetism via external stimuli. Herein, a field‐induced CoII single‐molecule magnet was found to exhibit the reversible switch of Jahn–Teller distortion near room temperature, along with thermal conformational motion of the 18‐crown‐6 rotor, which pulls the coordinated H2O to rotate through intermolecular hydrogen bonds and triggers a single‐crystal‐to‐single‐crystal phase transition with Twarm=282 K and Tcool=276 K. Interestingly, the molecular magnetic anisotropy probed by single‐crystal angular‐resolved magnetometry revealed the reorientation of easy axis by 14.6°. Moreover, ON/OFF negative magnetodielectric effects were respectively observed in the high‐/low‐temperature phase, which manifests the spin‐lattice interaction in the high‐temperature phase could be stronger, in accompanied by the hydrogen bonding between the rotating 18‐crown‐6 and the coordinated H2O.
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