The First Use of a ReX₅ Synthon to Modulate Fe^III Spin Crossover via Supramolecular Halogen⋅⋅⋅Halogen Interactions

Abstract

We have added the {ReIVX5}− (X=Br, Cl) synthon to a pocket‐based ligand to provide supramolecular design using halogen⋅⋅⋅halogen interactions within an FeIII system that has the potential to undergo spin crossover (SCO). By removing the solvent from the crystal lattice, we “switch on” halogen⋅⋅⋅halogen interactions between neighboring molecules, providing a supramolecular cooperative pathway for SCO. Furthermore, changes to the halogen‐based interaction allow us to modify the temperature and nature of the SCO event.

The role of intermolecular interactions in [Fe(X-salEen)2]ClO4 spin crossover complexes

“…1 While early studies primarily concentrated on intramolecular factors governing spin transitions, namely coordination sphere and ligand field strength, 2,3 it has become increasingly evident that intermolecular interactions play a crucial role in the cooperative behaviour and stability of SCO complexes in the solid state. [4][5][6][7] These interactions include hydrogen bonding, [8][9][10][11] π-π stacking, [12][13][14][15] halogen bonding, [16][17][18][19] and crystal packing effects, [20][21][22][23] which can drastically impact the thermodynamic and kinetic aspects of the SCO phenomenon.…”

Spin-Crossover Behaviors of Iron(II) Complexes Bearing Halogen Ligands in Solid State and Solution

“…Indeed, many functional materials based on halogen ligands have been developed in the past decades. However, in the field of SCO materials, the halogen atoms are mostly utilized via halogen substitution on various ancillary ligands or halogen bonds to tune the spin transition behaviors, but direct coordination of the halogen atoms to the metal center is much rare because their weak ligand-field strength is usually inadequate to actuate the SCO transitions. − Holzhacker et al reported two SCO Fe­(II) complexes bearing halogen ligands with a formula of [Fe II (PN H -Ph) 2 X 2 ] (PN H -Ph = N -diphenylphosphino-2-aminopyridine, X = Cl or Br) . However, these compounds suffer from the extreme air sensitivity of the tert -phosphine ligands.…”

Single-Molecule Magnet Properties in 3d4f Heterobimetallic Iron and Dysprosium Complexes Involving Hydrazone Ligand

“…In this context, the combination of Fe(II) or Fe(III) with Ln(III) is of particular interest and it already permitted the design of 3d4f SMMs [13][14][15][16][17][18]. The two ((E)-N -(2-hybroxy-3-methoxybenzylidene)pyrazine-2-carbohydrazide) (H 2 opch) (Scheme 1) and 1,2-Bis(2-hydroxy-3-methoxybenzylidene) hydrazine (H 2 bmh) (Scheme 1) ligands were selected because they were used to design lanthanide SMMs [19][20][21][22] and Fe(III) spin-crossover complexes [23].…”

“…The two ((E)-N′-(2-hybroxy-3-methoxybenzylidene)pyrazine-2-carbohydrazide) (H2opch) (Scheme 1) and 1,2-Bis(2-hydroxy-3-methoxybenzylidene) hydrazine (H2bmh) (Scheme 1) ligands were selected because they were used to design lanthanide SMMs [19][20][21][22] and Fe(III) spin-crossover complexes [23]. Scheme 1.…”