Guest‐, Light‐ and Thermally‐Modulated Spin Crossover in [FeII2] Supramolecular Helicates. Issue 25 (10th May 2016)

• Record Type: Journal Article
• Authors: Darawsheh, Mohanad; Barrios, Leoni A.; Roubeau, Olivier; Teat, Simon J.; Aromí, Guillem
• Is Part Of: Chemistry. Volume 22:Issue 25(2016)
• Page Start: 8635
• Page End: 8645
• Publication Date: 2016-05-10
• Subjects: coordination chemistry -- crystallography -- iron(II) helicates -- spin crossover -- supramolecular chemistry; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201601080
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: A new bis(pyrazolylpyridine) ligand (H2 L) has been prepared to form functional [Fe2 (H2 L)3 ] 4+ metallohelicates. Changes to the synthesis yield six derivatives, X@[Fe2 (H2 L)3 ]X(PF6 )2 ⋅ x CH3 OH (1, x =5.7 and X=Cl;2, x =4 and X=Br), X@[Fe2 (H2 L)3 ]X(PF6 )2 ⋅ y CH3 OH⋅H2 O (1 a, y =3 and X=Cl;2 a, y =1 and X=Br) and X@[Fe2 (H2 L)3 ](I3 )2 ⋅3 Et2 O (1 b, X=Cl;2 b, X=Br). Their structure and functional properties are described in detail by single‐crystal X‐ray diffraction experiments at several temperatures. Helicates1 a and2 a are obtained from1 and2, respectively, by a single‐crystal‐to‐single‐crystal mechanism. The three possible magnetic states, [LS–LS], [LS–HS], and [HS–HS] can be accessed over large temperature ranges as a result of the structural nonequivalence of the Fe II centers. The nature of the guest (Cl − vs. Br − ) shifts the spin crossover (SCO) temperature by roughly 40 K. Also, metastable [LS–HS] or [HS–HS] states are generated through irradiation. All helicates (X@[Fe2 (H2 L)3 ]) 3+ persist in solution. Abstract : Host–guest interactions shift spin crossover : A new bis(pyrazolylpyridine) ligand (H2 L) has been used to prepare six functional X@[Fe2 (H2 L)3 ] 3+ metallohelicates with entrapped guest ions (X=Cl, Br). Spin crossover between three magnetic states [LS–LS], [LS–HS], and [HS–HS] of the dinuclear Fe II supramolecular helicates could be accessed by thermal or chemical changes, solvate ‐molecule or guest‐ion exchange, and light irradiation.