Halobenzene Clathrates of the Porous Metal–Organic Spin-Crossover Framework [Fe(tvp)2(NCS)2] n . Stabilization of a Four-Step Transition

• Published in: Inorganic chemistry Vol. 61; no. 10; pp. 4484 - 4493
• Main Authors: Orellana-Silla, Alejandro, Valverde-Muñoz, Francisco Javier, Muñoz, M. Carmen, Bartual-Murgui, Carlos, Ferrer, Sacramento, Real, José Antonio
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 14.03.2022
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.2c00014

Here we show that the porous metal–organic spin crossover (SCO) framework [Fe­(tvp)2(NCS)2]@4­(CH3CN·H2O) [1@4­(CH 3 CN·H 2 O)] is an excellent precursor material for the systematic synthesis, via single-crystal to single-crystal transformation, of a series of halobenzene clathrates. Immersion of samples constituted of single crystals of 1@4­(CH 3 CN·H 2 O) in the liquid halobenzenes PhX n , X = F (n = 1–6), X = Cl (n = 1, 2), and X = Br (n = 1) at room temperature induces complete replacement of the guest molecules by PhX n to afford 1@2PhX n . Single-crystal analyses of the new clathrates confirm the integrity of the porous framework with the PhX n guests being organized by pairs via π-stacking filling the nanochannels. The magnetic and calorimetric data confirm the occurrence of practically complete SCO behavior in all of the clathrates. The characteristic SCO equilibrium temperatures, T 1/2, seem to be the result of a subtle balance in the host–guest interactions, which are temperature- and spin-state-dependent. The radically distinct supramolecular organization of the PhCl2 guests in 1@2PhCl 2 affords a rare example of four-step SCO behavior following the sequence [HS1:LS0] ↔ [HS2/3:LS1/3] ↔ [HS 1/2:LS 1/2] ↔ [HS1/4:LS3/4] ↔ [HS0:LS1], which has been structurally characterized.