scholarly journals Symmetry breaking above room temperature in an Fe(ii) spin crossover complex with an N4O2 donor set

2017 ◽  
Vol 53 (8) ◽  
pp. 1374-1377 ◽  
Author(s):  
Wasinee Phonsri ◽  
Casey G. Davies ◽  
Guy N. L. Jameson ◽  
Boujemaa Moubaraki ◽  
Jas S. Ward ◽  
...  
Keyword(s):  
Symmetry Breaking ◽  
Room Temperature ◽  
Spin Crossover ◽  
Variable Temperature ◽  
Spin Transition ◽  
Temperature Variable

An halogen-substituted salicylaldimine iron(ii) complex shows an abrupt two-step spin transition above room temperature, variable temperature crystallography showing symmetry breaking.

scholarly journals High-temperature Spin Crossover of a Solvent-Free Iron(II) Complex with the Linear Hexadentate Ligand [Fe(L2-3-2Ph)](AsF6)2 (L2-3-2Ph = bis[N-(1-Phenyl-1H-1,2,3-triazol-4-yl)methylidene-2-aminoethyl]-1,3- propanediamine)

2019 ◽  
Vol 5 (1) ◽  
pp. 10 ◽  
Author(s):  
Hiroaki Hagiwara
Keyword(s):  
Room Temperature ◽  
Spin Crossover ◽  
Variable Temperature ◽  
Spin Transition ◽  
Three Dimensional ◽  
Solvent Free ◽  
Supramolecular Network ◽  
Scanning Calorimetry ◽  
Mononuclear Iron ◽  
3D Network

A novel mononuclear iron(II) complex with a linear hexadentate N6 ligand, containing two 1,2,3-triazole moieties, [Fe(L2-3-2Ph)](AsF6)2 (1), was synthesized (L2-3-2Ph = bis[N-(1-Phenyl-1H-1,2,3-triazol-4-yl)methylidene-2-aminoethyl]-1,3-propanediamine). Variable-temperature magnetic susceptibility measurements revealed a gradual one-step spin crossover (SCO) between the high-spin (HS, S = 2) and low-spin (LS, S = 0) states above room temperature (T1/2 = 468 K). The spin transition was further confirmed by differential scanning calorimetry (DSC). A single-crystal X-ray diffraction study showed that the complex was in the LS state (S = 0) at room temperature (296 K). In the crystal lattice, a three-dimensional (3D) supramolecular network was formed by intermolecular CH⋯ and – interactions of neighboring complex cations [Fe(L2-3-2Ph)]2+. AsF6− ions were located interstitially in the 3D network of complex cations, with no solvent-accessible voids. The crystal structure at 448 K (mixture of HS and LS species) was also successfully determined thanks to the thermal stability of the solvent-free crystal.

One Shot Laser Pulse Induced Reversible Spin Transition in the Spin-Crossover Complex [Fe(C4H4N2){Pt(CN)4}] at Room Temperature

2005 ◽  
Vol 117 (26) ◽  
pp. 4137-4141 ◽  
Author(s):  
Sébastien Bonhommeau ◽  
Gábor Molnár ◽  
Ana Galet ◽  
Antoine Zwick ◽  
José-Antonio Real ◽  
...  
Keyword(s):  
Laser Pulse ◽  
Room Temperature ◽  
Spin Crossover ◽  
Spin Transition

Towards direct correlations between spin-crossover and structural features in iron(II) complexes

2003 ◽  
Vol 59 (4) ◽  
pp. 479-486 ◽  
Author(s):  
Mathieu Marchivie ◽  
Philippe Guionneau ◽  
Jean-François Létard ◽  
Daniel Chasseau
Keyword(s):  
Crystal Structures ◽  
Room Temperature ◽  
Spin Crossover ◽  
Spin Transition ◽  
Intermolecular Hydrogen Bond ◽  
Structural Features ◽  
Gradual Transition ◽  
Hydrogen Bond Interaction ◽  
First Approximation ◽  
Two Phases

The [Fe(PM-BiA)2(NCS)2] complex, where PM is N-2-pyridylmethylene and BiA is 4-aminobiphenyl, crystallizes in two polymorphs. The two phases, denoted (I) and (II), undergo a spin-crossover when the sample is cooled and present distinct spin-transition features as (I) shows a very abrupt spin transition, while (II) exhibits a gradual transition. The two forms of the complex are used to investigate the correlations that exist between the spin-transition features and structural features. This article presents the crystal structures of polymorph (II) at room temperature (high spin) and at 120 K (low spin), including a comparison with those of polymorph (I). This study reveals that the packing, in a first approximation, is similar in both forms. In order to look at the crystal structures in more detail, a new angular parameter, denoted θNCS, as well as a particular type of intermolecular hydrogen-bond interaction, which involves the S atoms of the NCS ligands, are investigated. Interestingly, this angle and this intermolecular interaction can be directly connected to the cooperativity of the spin transition. Such a result is extended to all the SCO iron(II) complexes belonging to the same family of the general formula [Fe(PM-L)2(NCS)2].

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

Symmetry ◽  
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.

scholarly journals Hysteretic Thermal Spin-Crossover and Symmetry Breaking in Heteroleptic Fe(II) Complexes Using Alkyl Chain Substituted 2,2’-Dipyridylamine Ligands

2019 ◽  
Author(s):  
Blaise Geoghegan ◽  
Wasinee Phonsri ◽  
Peter Horton ◽  
James Orton ◽  
Simon Coles ◽  
...  
Keyword(s):  
Phase Transition ◽  
Spin Crossover ◽  
Alkyl Chain ◽  
Thermal Hysteresis ◽  
Variable Temperature ◽  
Spin Transition ◽  
Magnetic Data ◽  
Monoclinic Space Group ◽  
Space Group ◽  
Bond Lengths

The alkyl chain carrying ligands N,N-di(pyridin-2-yl)butanamide (LC4) and N,N-di(pyridin-2-yl)decanamide (LC10) were combined with NCS- co-ligands to form the neutral heteroleptic Fe(II) complexes trans-[FeII(LC4)2(NCS)2] (1C4) and trans [FeII(LC10)2(NCS)2] (1C10). Variable temperature crystallographic studies revealed that 1C4 is in the orthorhombic space group Pna21 between 85-200 K whereas 1C10 is in the monoclinic space group P21/c between 85-105 K before undergoing a crystallographic phase transition to the triclinic space group P1􀴤 by 140 K. The average Fe-N bond lengths suggest that at 85 K 1C4 contains LS Fe(II) centres; However, the ca. 0.18 Å increase in the average Fe-N bond lengths between 85 and 120 K suggests a spin-transition occurs within this temperature interval and the HS state is predominant beyond this. 1C10 contains LS Fe(II) centres between 85 and 105 K. Upon warming from 105 to 140 K the average Fe-N bond lengths increase by ca. 0.19 Å, which suggests that a spin-transition to the HS accompanies the P21/c to P1􀴤 crystallographic phase transition. Solid-state magnetic susceptibility measurements showed that 1C4 undergoes semi-abrupt spin-crossover with T1/2 = 127.5 K and a thermal hysteresis of ca. 13 K whereas, 1C10 undergoes an abrupt spin-crossover with T1/2 = 119.0 K, and is also accompanied by thermal hysteresis of ca. 4 K. The crystallographic and magnetic data show that the length of the complex’s alkyl chain substituents can have a large impact on the structure of the crystal lattice as well as a subtle effect on the T1/2 value for thermal spin-crossover.

Titelbild: One Shot Laser Pulse Induced Reversible Spin Transition in the Spin-Crossover Complex [Fe(C4H4N2){Pt(CN)4}] at Room Temperature (Angew. Chem. 26/2005)

2005 ◽  
Vol 117 (26) ◽  
pp. 4011-4011 ◽  
Author(s):  
Sébastien Bonhommeau ◽  
Gábor Molnár ◽  
Ana Galet ◽  
Antoine Zwick ◽  
José-Antonio Real ◽  
...  
Keyword(s):  
Laser Pulse ◽  
Room Temperature ◽  
Spin Crossover ◽  
Spin Transition

One Shot Laser Pulse Induced Reversible Spin Transition in the Spin-Crossover Complex [Fe(C4H4N2){Pt(CN)4}] at Room Temperature

2005 ◽  
Vol 44 (26) ◽  
pp. 4069-4073 ◽  
Author(s):  
Sébastien Bonhommeau ◽  
Gábor Molnár ◽  
Ana Galet ◽  
Antoine Zwick ◽  
José-Antonio Real ◽  
...  
Keyword(s):  
Laser Pulse ◽  
Room Temperature ◽  
Spin Crossover ◽  
Spin Transition
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