Iron(II) Spin Crossover Polymers of Planar N2O2 Schiff Base Templates and 4,4’-bis(pyridyl)urea Bridges

Introduction:The synthesis of four new iron(II) coordination polymers [Fe(L1a)(bpua)] (1), [Fe(L1b)(bpua)](0.5bpua) (2), [Fe(L2a)(bpua)] (3), [Fe(L1b)(bpua)](yEtOH) (5) and one trinuclear complex [{Fe(L1a)(bpua)(MeOH)}2-µ{Fe(L1a)}](xMeOH) (4) with Schiff base-like N2O2coordinating equatorial ligands (L1a, L1b and L2a) and 4,4’-bis(pyridyl)urea (bpua) as bridging axial ligand is described.Materials and Methods:Single crystal X-ray structure elucidation of the trinuclear module4and of the coordination polymer5reveals the presence of HS-LS-HS chains and all-HS infinite 1-D strands, respectively. As anticipated the presence of the bridging urea supports the supramolecular concatenation within an extended hydrogen-bonding network. Magnetic measurements reveal spin crossover behavior for four of the five complexes (1–4) that is strongly solvent dependent.Results and Conclusion:Interestingly, in two cases, complete removal of the solvent from the crystal packing leads to wider thermal hysteresis loops.

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Iron(II) Spin Crossover Complexes with 4,4′-Dipyridylethyne—Crystal Structures and Spin Crossover with Hysteresis

Molecules ◽

10.3390/molecules25030581 ◽

2020 ◽

Vol 25 (3) ◽

pp. 581 ◽

Cited By ~ 1

Author(s):

Katja Dankhoff ◽

Charles Lochenie ◽

Birgit Weber

Keyword(s):

Coordination Polymers ◽

Spin Crossover ◽

Thermal Hysteresis ◽

Hysteresis Loops ◽

Structure Property ◽

Crossover Behavior ◽

Structure Property Relationship ◽

Wide Hysteresis ◽

Xrd Patterns ◽

Relationship Of

Three new iron(II) 1D coordination polymers with cooperative spin crossover behavior showing thermal hysteresis loops were synthesized using N2O2 Schiff base-like equatorial ligands and 4,4′-dipyridylethyne as a bridging, rigid axial linker. One of those iron(II) 1D coordination polymers showed a 73 K wide hysteresis below room temperature, which, upon solvent loss, decreased to a still remarkable 30 K wide hysteresis. Single crystal X-ray structures of two iron(II) coordination polymers and T-dependent powder XRD patterns are discussed to obtain insight into the structure property relationship of those materials.

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Spin-crossover in an iron(iii) complex showing a broad thermal hysteresis

Dalton Transactions ◽

10.1039/d0dt03610b ◽

2021 ◽

Author(s):

Cyril Rajnák ◽

Romana Mičová ◽

Ján Moncoľ ◽

Ľubor Dlháň ◽

Christoph Krüger ◽

...

Keyword(s):

Schiff Base ◽

Schiff Base Ligand ◽

Spin Crossover ◽

Thermal Hysteresis ◽

Mononuclear Complex ◽

Hysteresis Width ◽

Thermally Induced

A pentadentate Schiff-base ligand 3,5Cl-L2− and NCSe− form a iron(iii) mononuclear complex [Fe(3,5Cl-L)(NCSe)], which shows a thermally induced spin crossover with a broad hysteresis width of 24 K between 123 K (warming) and 99 K (cooling).

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Compensation effects and relation between the activation energy of spin transition and the hysteresis loop width for an iron(ii) complex

Physical Chemistry Chemical Physics ◽

10.1039/c6cp01892k ◽

2016 ◽

Vol 18 (25) ◽

pp. 16690-16699 ◽

Cited By ~ 11

Author(s):

Mark B. Bushuev ◽

Denis P. Pishchur ◽

Elena B. Nikolaenkova ◽

Viktor P. Krivopalov

Keyword(s):

Hysteresis Loop ◽

Spin Crossover ◽

Thermal Hysteresis ◽

Activation Barrier ◽

Spin Transition ◽

Hysteresis Loops ◽

High Activation ◽

Activation Barriers ◽

Spin Crossover Complexes ◽

Hysteresis Loop Width

Wide thermal hysteresis loops for iron(ii) spin crossover complexes are associated with high activation barriers: the higher the activation barrier, the wider the hysteresis loop for a series of related spin crossover systems.

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Evidence of Photo-Thermal Effects on the First-Order Thermo-Induced Spin Transition of [{Fe(NCSe)(py)2}2(m-bpypz)] Spin-Crossover Material

Magnetochemistry ◽

10.3390/magnetochemistry5020021 ◽

2019 ◽

Vol 5 (2) ◽

pp. 21 ◽

Cited By ~ 1

Author(s):

Kamel Boukheddaden ◽

Houcem Fourati ◽

Yogendra Singh ◽

Guillaume Chastanet

Keyword(s):

Thermal Effects ◽

Spin Crossover ◽

Evolution Equations ◽

Thermal Hysteresis ◽

Magnetic Measurements ◽

Equations Of Motion ◽

Spin Transition ◽

Thermal Bath ◽

Trapping Region ◽

First Order

We have investigated by means of optical microscopy and magnetic measurements the first-order thermal spin transition of the [{Fe(NCSe)(py)2}2(m-bpypz)] spin-crossover compound under various shining intensities, far from the light-induced spin-state trapping region. We found evidence of photo-heating effects on the thermally-induced hysteretic response of this spin-crossover material, thus causing the shift of the thermal hysteresis to lower temperature regions. The experimental results are discussed in terms of the apparent crystal temperature and are analyzed theoretically using two evolution equations of motion, written on the high-spin (HS) fraction and heat balance between the crystal and the thermal bath. A very good qualitative agreement was found between experiment and theory in the stationary regime, explaining the experimental observations well and identifying the key factors governing these photo-thermal effects.

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A Promising New Schiff Base-like Ligand for the Synthesis of Octahedral Iron(II) Spin Crossover Complexes

Zeitschrift für Naturforschung B ◽

10.1515/znb-2010-0315 ◽

2010 ◽

Vol 65 (3) ◽

pp. 323-328 ◽

Cited By ~ 17

Author(s):

Wolfgang Bauer ◽

Tanja Ossiander ◽

Birgit Weber

Keyword(s):

Schiff Base ◽

High Spin ◽

Spin Crossover ◽

Magnetic Measurements ◽

X Ray ◽

X Ray Crystallography ◽

Tetradentate Schiff Base ◽

Spin Crossover Complexes

A new tetradentate Schiff base-like ligand H2L (1) ((E,E)-dimethyl-2,2´-[1,2-phenylenebis(aminomethylidyne)] bis[3-oxobutanoate]) was synthesised and structurally characterised. Its reaction with iron(II) acetate leads to the formation of the octahedral N2O4-coordinated complex [FeL(MeOH)2] (2). The complex is a pure high-spin (HS) compound as is evident from magnetic measurements and X-ray crystallography.

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Elastic Origin of the Unsymmetrical Thermal Hysteresis in Spin Crossover Materials: Evidence of Symmetry Breaking

Symmetry ◽

10.3390/sym13050828 ◽

2021 ◽

Vol 13 (5) ◽

pp. 828

Author(s):

Mamadou Ndiaye ◽

Nour El Islam Belmouri ◽

Jorge Linares ◽

Kamel Boukheddaden

Keyword(s):

Symmetry Breaking ◽

High Spin ◽

Spin Crossover ◽

Thermal Hysteresis ◽

Spin Transition ◽

Hysteresis Loops ◽

Point Of View ◽

Self Organization ◽

Spin States ◽

Heating And Cooling

The jungle of experimental behaviors of spin-crossover materials contains a tremendous number of unexpected behaviors, among which, the unsymmetrical hysteresis loops having different shapes on heating and cooling, that we often encounter in literature. Excluding an extra effect of crystallographic phase transitions, we study here these phenomena from the point of view of elastic modeling and we demonstrate that a simple model accounting for the bond lengths misfits between the high-spin and low-spin states is sufficient to describe the situation of unsymmetrical hysteresis showing plateaus at the transition only on cooling or on heating branches. The idea behind this effect relates to the existence of a discriminant elastic frustration in the lattice, which expresses only along the high-spin to low-spin transition or in the opposite side. The obtained two-step transitions showed characteristics of self-organization of the spin states under the form of stripes, which we explain as an emergence process of antagonist directional elastic interactions inside the lattice. The analysis of the spin state transformation inside the plateau on cooling in terms of two sublattices demonstrated that the elastic-driven self-organization of the spin states is accompanied with a symmetry breaking.

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Design of Bistable Gold@Spin-Crossover Core-Shell Nanoparticles Showing Large Electrical Responses for the Spin Switching

10.26434/chemrxiv.7543121 ◽

2019 ◽

Author(s):

Ramón Torres-Cavanillas ◽

Rocher Sanchis-Gual ◽

Julien Dugay ◽

Marc Coronado-Puchau ◽

Dr. Mónica Giménez Marqués ◽

...

Keyword(s):

Spin Crossover ◽

Thermal Hysteresis ◽

Spin Transition ◽

Hysteresis Loops ◽

Large Change ◽

Core Shell ◽

Shell Nanoparticles ◽

Simple Protocol ◽

Order Of Magnitude ◽

Core Shell Nanoparticles

A simple protocol to prepare core-shell gold@spin-crossover (Au@SCO) nanoparticles (NPs) based on the 1D spin-crossover [Fe(Htrz)2(trz)](BF4) coordination polymer is reported. The synthesis relies on a two-step approach consisting on a partial surface ligand substitution of the citrate-stabilized Au NPs followed by the controlled growth of a very thin layer of the SCO polymer. As a result, colloidally stable core@shell spherical NPs of 19 nm in size exhibiting a narrow distribution in sizes have been obtained, revealing a switchable SCOshell of ca.4 nm. Temperature-dependent charge transport measurements of an electrical device based on assemblies of these Au@SCO NPs display well-defined, reproducible and sharp thermal hysteresis loops in the conductance near room temperature. This device is characterized both, by a large change in conductance upon spin state switching, and a remarkable transition abruptness, as compared with other memory devices based on the pristine SCO NPs. As a result, the sensitivity of the device to the spin transition is dramatically improved, with values for the ON/OFF ratio which are an order of magnitude better than the best ones obtained in previous SCO devices.

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