Pressure and temperature induced high spin–low spin phase transition: Macroscopic and microscopic consideration

Levchenko, G. G.; Khristov, A. V.; Kuznetsova, V. V.; Shelest, V. V.

doi:10.1016/j.jpcs.2014.04.006

Cited by 18 publications

(26 citation statements)

References 39 publications

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“…Figure 10 shows cyanide-based SCO polymers. Recently, a theoretical study has demonstrated that the changes of the elastic and inelastic forces in the crystal as a function of pressure or temperature determine the behaviour of the spin transition in these polymers [132,148].…”

Section: Compounds With Abrupt Thermal Spin Transition Accompanied Wimentioning

confidence: 99%

Pressure effect investigations on spin-crossover coordination compounds

Gaspar

Molnár

Rotaru

et al. 2018

Comptes Rendus. Chimie

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The piezo-chromic properties of spin crossover complexes have been recognized for a long time, with increasing pressure favouring the low spin state due to its smaller volume and therefore shifting the spin equilibrium towards higher temperatures and accelerating the relaxation at a given temperature. However, the interpretation and quantification of pressure induced changes have been several times compromised by the relatively poor and incomplete spectral and structural information provided by the detection methods or due to the experimental difficulties related to the need for hydrostatic conditions at low temperatures. The present review is therefore primarily focused on these experimental aspects of high pressure spin crossover research providing an overview of methods of pressure generation and associated detection methods as well as on selected recent results.Résumé: Les propriétés piézo-chromiques de complexes à transition de spin ont été identifiées depuis longtemps. Du point de vue théorique, l'application d'une pression favorise l'état bas spin, de plus petit volume. Ainsi les températures de transition augmentent et les cinétiques de relaxation s'accélèrent sous pression. Toutefois, l'interprétation et la quantification des modifications induites par la pression restent un challenge en raison de la difficulté d'obtenir des données structurales et spectrales fiables dans des conditions de pression hydrostatique. Ceci est d'autant plus vrai lorsque les hautes pressions et les basses températures doivent être combinées. Ainsi, l'objectif principal du présent article est une mise au point sur les techniques utilisées pour l'étude des composés à transition de spin sous pressionillustrées par une sélection de résultats récents.the piston(s) in the desired position even after removing the cell from the press. These (relatively) small, autonomous cells are particularly popular because they can be easily combined with cryostats, magnetometers and other equipment [26,82,109]. While several designs, both home built and commercially available have been used in the study of SCO materials, the principle upon which they work is similar. In general the sample is placed in a Teflon capsule J Rotaru et al. have been analysed the thermal behaviour of the spin transition complexes [FexZn1-x(btr)2(NCS)2]H2O (for x=0.6 and x=1) by diffuse reflectivity measurements, under constant pressure in the range 1-1600 bars obtained with a gas pressure cell [186]. I J , as shown in Figure 24.

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Section: Compounds With Abrupt Thermal Spin Transition Accompanied Wimentioning

confidence: 99%

Pressure effect investigations on spin-crossover coordination compounds

Gaspar

Molnár

Rotaru

et al. 2018

Comptes Rendus. Chimie

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“…Note that special states with charge transfer in ligand complex are present and also a special role of π-coupling in SC process is observed [24,29]. It is known that besides hydrogen couplings connecting both the polymeric chains and the complexes, π-coupling in SC systems, especially in polymers, intensifies the cooperativity and influences the hysteresis loop width [14, 30, [4][5][6][7][8][9][10]), are, first of all, radiationless transitions stipulated by internal conversion and intersystem crossing, which are directly connected with mutual influence of electronic and phonon subsystems including spin-orbital coupling in the case of presence of electronic states with intermediate multiplicity [20,26].…”

Section: Micro-and Macroaspects Of Scmentioning

confidence: 99%

“…Points of bend (influction points on C p (T) curve) conditionally assign a PCT range with maximal development of fluctuations, cutting off on C p (T) curve the corresponding segments with concavity and salience. Actually, fluctuation maximum is reached in the transition point T c =T 1/2 [4][5][6][7][8][9][10]. At the time point of bend T max (extremal point on C p (T max ) curve -T max ≠T c -influction point on ρ H (T c ) curve -"function distribution" (statistical weight ρ H ≤1) of spin states HS phase) [10] can be equal to T 1/2 symbolically only.…”

Section: Fig 2 Entropy Dependence On Temperature: 1 -[Fe(hyptrz)3]amentioning

confidence: 99%

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Non-Conventional Standpoint on Spin Crossovers in the Organometallic Compounds of Iron Group

Shelest¹

2015

JPMT

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Abstract:We have considered the spin crossover (SC) complex compounds containing spin-active metal ions of iron group, which can induce the spin transitions (ST) of high spin (HS) -low spin (LS) type under influence of temperature (TIST), pressure (PIST) or light (LIESST) from non-conventional point of view. We have analyzed the physical peculiarities of the studied ST systems observed in numerous papers for X ray, spectral, calorimetric and magnetic measurements. On this basis, we suppose that ST (for example, in bulk of SC compounds with TIST) can be considered as phase transitions (PT) of postcritical type (PCT).

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“…13 These studies were conducted chiefly with Fe(II) compounds, which are typically the most cooperative SCO materials, owing to their larger volume change on SCO. [14][15][16][17] Such studies on Fe(III) compounds are less frequent, 18,19 especially those which exhibit a first-order spin transition. 20 In this context, the possibility of generating cooperative elastic interactions that drive the self-amplification of the spin-state switching in the out-of-equilibrium state of a SCO solid was recently demonstrated by using ultrafast laser excitation.…”

Section: Introductionmentioning

confidence: 99%

Pressure-induced switching properties of the iron(iii) spin-transition complex [Fe^III(3-OMeSalEen)₂]PF₆

Laisney

Shepherd

Rechignat

et al. 2018

Phys. Chem. Chem. Phys.

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We investigated the effect of an externally applied pressure on the iron(iii) Schiff-base compound [Fe(3-OMeSalEen)2]PF6 (H-3-OMeSalEen, condensation product of 3-methoxy-substituted salicylaldehyde and N-ethylethylenediamine), which at ambient pressure displays a thermal spin transition with a 3 K wide hysteresis loop centered at 164 K. Raman spectrometry revealed the occurrence of a complete spin-state switching process for a pressure of P1/2 = 8-9 kbar at room temperature. The evolution of lattice parameters as a function of pressure was followed by X-ray diffraction measurements on single crystals, highlighting the important microscopic aspects at the origin of the pressure-induced transition, i.e. an anisotropic response and a high compressibility of the HS molecular lattice. Variable temperature magnetic susceptibility measurements at different applied pressures revealed the smoothening of the spin transition curves and a linear increase of the transition temperatures by ca. 16.4 (1.0) K kbar-1, in good agreement with the Clausius-Clapeyron law. The non-negligible influence of the pressure transmitting oils on the intrinsic transition properties was also evidenced and attributed to mechanical interactions between the particles and the solidified matrix.

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Pressure and temperature induced high spin–low spin phase transition: Macroscopic and microscopic consideration

Cited by 18 publications

References 39 publications

Pressure effect investigations on spin-crossover coordination compounds

Pressure effect investigations on spin-crossover coordination compounds

Non-Conventional Standpoint on Spin Crossovers in the Organometallic Compounds of Iron Group

Pressure-induced switching properties of the iron(iii) spin-transition complex [Fe^III(3-OMeSalEen)₂]PF₆

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Pressure and temperature induced high spin–low spin phase transition: Macroscopic and microscopic consideration

Cited by 18 publications

References 39 publications

Pressure effect investigations on spin-crossover coordination compounds

Pressure effect investigations on spin-crossover coordination compounds

Non-Conventional Standpoint on Spin Crossovers in the Organometallic Compounds of Iron Group

Pressure-induced switching properties of the iron(iii) spin-transition complex [FeIII(3-OMeSalEen)2]PF6

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Pressure-induced switching properties of the iron(iii) spin-transition complex [Fe^III(3-OMeSalEen)₂]PF₆