Multistability at Room Temperature in a Bent-Shaped Spin-Crossover Complex Decorated with Long Alkyl Chains

Abstract

An iron(II) pyridyl-benzohydrazonate-based complex decorated with long alkyl chains is reported as a rare spin-crossover compound displaying a wide thermal hysteresis spanning room temperature. On heating, this compound exhibits a spin transition between a LS ground state and an ordered HS-LS phase with symmetry breaking from monoclinic P2/n into orthorhombic P222 space groups. During cooling, the compound first transits into a magnetically distinguishable HS-LS phase with monoclinic P2 symmetry before returning into the LS phase. Interconversion between the two distinct HS-LS phases is the result of subtle structural changes in the alkyl chains and produces a second minor thermal hysteresis that superposes to the large one. This unprecedented result shows that the combination of a conventional cooperative spin transition and ligand-driven magnetic changes can promote magnetic tristability at room temperature.

Enhanced dielectricity coupled to spin-crossover in a one-dimensional polymer iron(ii) incorporating tetrathiafulvalene

“…The average Fe1–N and Fe1–N bpy bond lengths are 1.982 and 2.100 Å, respectively, and lie within the range reported for low-spin Fe II (Fe1) compounds. 3c , 12 …”

Spin Crossover in 3D Metal Centers Binding Halide-Containing Ligands: Magnetism, Structure and Computational Studies

“…In solution, the distribution of spin states is assigned using a Boltzmann distribution, and a spin equilibrium is expected at different temperatures. However, depending on the nature of the ligand used, interactions between molecules may occur and SCO systems with different degrees of communication between metal centers have sometimes been reported [50][51][52][53][54][55]. The molecules deposited on supports have been subjected to electric fields to produce systems that change their spin state by an application of a more suitable stimulus towards application into spintronics [47][48][49][56][57][58][59][60].…”

Spatiotemporal Studies of the One‐Dimensional Coordination Polymer [Fe(ebtz)2(C2H5CN)2](BF4)2: Tug of War between the Nitrile Reorientation Versus Crystal Lattice as a Tool for Tuning the Spin Crossover Properties**

“…[4a] Thus, crystal packing effects hamper the control of spin crossover properties, yet the of coupling between crystal lattice and electronic properties of the spin crossover centers, resulting from the structure of the first coordinations phere, becomes an origin of unexpected behavior.T he most striking example is the reverse spin crossover in Co II and Fe II complexes triggered by phase transitions associatedw ith significant structural reorganization [25] in which the crucial role is playedb y conformational changes of the alkyl chains. [26] Conformational changes may involvee ven more subtle alterations leading, in mononuclear systems, to tristability depending on presence of "hysteresis within hysteresis" [27] or to the occurrence of two memory channels, whichc an be addressed separately by choosingt he temperature scan rate. [28] It is worth notingt hat in some cases,u ncommon spin transitions may result also from kinetic effects.…”

“…The most striking example is the reverse spin crossover in Co II and Fe II complexes triggered by phase transitions associated with significant structural reorganization [25] in which the crucial role is played by conformational changes of the alkyl chains [26] . Conformational changes may involve even more subtle alterations leading, in mononuclear systems, to tristability depending on presence of “hysteresis within hysteresis” [27] or to the occurrence of two memory channels, which can be addressed separately by choosing the temperature scan rate [28] . It is worth noting that in some cases, uncommon spin transitions may result also from kinetic effects [29] …”