The Role of Binary and Many-Centre Molecular Interactions in Spin Crossover in the Solid State. Part IV. Ordering in Systems with Many-Body Interactions

Koudriavtsev, Andrei B.; Jameson, R. F.; Linert, Wolfgang

doi:10.1007/s00706-006-0533-x

Cited by 13 publications

(5 citation statements)

References 24 publications

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“…Several models have been proposed to explain the occurrence of two-step SCO, which all account for a 1:1 HS/LS ratio in the IP. 58,[63][64][65][66][67][68] In particular, the [HS…”

Section: Discussionmentioning

confidence: 99%

“…Several models have been proposed to explain the occurrence of two-step SCO, which all account for a 1:1 HS/LS ratio in the IP. ,− In particular, the [HS···HS] ↔ [HS···LS] ↔ [LS···LS] symmetry-broken phase transition of [Fe(2-pic) 3 ]Cl 2 ·EtOH has been modeled soon after the observation of the [HS···LS] IP of this compound . The existence of the IP is seen as a result of competitive effects between local (antiferromagnetic-like intradimer coupling) and long-range elastic interactions.…”

Section: Discussionmentioning

confidence: 99%

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Influence of Sample Preparation, Temperature, Light, and Pressure on the Two-Step Spin Crossover Mononuclear Compound [Fe(bapbpy)(NCS)₂]

et al. 2009

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The three phases of the mononuclear two-step spin crossover compound [Fe(bapbpy)(NCS)2] (1) are characterized by powder X-ray diffraction, Mössbauer spectroscopy, Raman spectroscopy, calorimetry, and magnetic susceptibility measurements. Mössbauer and Raman spectroscopies confirm the results obtained from previous single crystal X-ray diffraction studies, as they show that the intermediate phase is characterized by a 1:2 high-spin/low-spin ratio and that it is not a mixture of the high-spin state (HS) and low-spin state (LS) phases. Sample preparation and sample history studies show that the spin crossover (SCO) properties of this compound are quite robust, as the two steps and hysteresis cycles are present both in the powder and in recrystallized samples and conserved when the sample is cooled and heated several times. Compound 2, a DMF solvate having the formula [Fe(bapbpy)(NCS)2]·2DMF, shows SCO properties but no cooperative effects. The origin of the strong cooperativity found in compound 1 is discussed. Finally, external perturbations have been applied to compound 1. First, light irradiation at low temperatures promotes the LS → HS transition with reasonably good optical conversions [∼70%, T(LIESST) = 56 K]. Second, the application of hydrostatic pressure increases both the temperature and the hysteresis width of the higher-temperature transition (HS ↔ IP), while unexpectedly suppressing the lower-temperature transition (IP ↔ LS).

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“…Several models have been proposed to explain the occurrence of two-step SCO, which all account for a 1:1 HS/LS ratio in the IP. 58,[63][64][65][66][67][68] In particular, the [HS…”

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Influence of Sample Preparation, Temperature, Light, and Pressure on the Two-Step Spin Crossover Mononuclear Compound [Fe(bapbpy)(NCS)₂]

et al. 2009

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“…Moreover, in the case of ethanol, an intermediate phase (IP) appears, whose origin has been ascribed to the coupling of the spin transition to an order−disorder phase transition of the solvent molecules . This system became a prototype for studies of the cooperativity of SCO molecules using phenomenological models ,,, and led to the development of an elaborated Ising model that accounted for both the spin- and the order–disorder phase transitions . Compound 1 allows us to test the performance of our protocol to describe the same SCO system presenting either a gradual or an abrupt transition under different environments.…”

Section: Introductionmentioning

confidence: 99%

Cooperativity in Spin Crossover Systems. An Atomistic Perspective on the Devil’s Staircase

Vela

Paulsen

2018

Inorg. Chem.

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Cooperativity is key in defining the shape (i.e., gradual, abrupt, or hysteretic) of thermally driven spin transitions in magnetic switches. Despite its importance, there is very little information on its atomistic origin, which hinders the rational design of materials displaying a bistability region (i.e., hysteresis). In this paper, we investigate the spin transition of two solvatomorphs of [Fe(2-pic)]Cl, an Fe(II)-complex displaying thermal spin crossover (SCO) from a low-spin (LS) to a high-spin (HS) state with either gradual or abrupt two-step character. To do it, we apply a novel computational protocol to study the cooperativity of SCO compounds from DFT calculations, which does not rely on a priori assumptions on the studied system. The distinct shape of the spin transition is successfully captured, and the atomistic origin of cooperativity is traced back to geometrical distortions of the Fe-N core in case of the solvatomorph exhibiting an abrupt transition. According to our calculations, HS and LS molecules contribute differently to cooperativity, which results in a complex energetic evolution of the spin transition that cannot be described by the common Slichter-Drickamer model. The present work opens new avenues for the study of cooperativity of SCO systems having a chemically oriented perspective and demonstrates that quantum chemistry calculations can discriminate the shape of a spin transition, while providing insight into the atomistic underlying factors that contribute to its cooperative behavior.

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“…10 There are a number of theoretical approaches developed to describe a classical spin crossover. 11 Most of the current theoretical treatments of cooperative effects in spin crossover are based on a variety of modifications to either the mean field approximation 12,13 (MFA) or computer simulations. 14 With decreasing temperature, the classical spin crossover may be either smooth 1,4 or abrupt, 1,15 which is unfeasible for the d 9 electron configuration of metal ions corresponding to Cu(II) complexes.…”

Section: Introductionmentioning

confidence: 99%

Cooperative spin-crossover-like transitions in the inhomogeneous chain of exchange clusters

Mоrоzоv

2013

Phys. Chem. Chem. Phys.

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A statistical theory of temperature-induced spin-crossover-like transitions has been developed for spin chains with a few exchange clusters in a unit cell. Using static magnetic susceptibility measurements, a general expression for the effective magnetic moment μ(eff) of exchange clusters is obtained for an arbitrary structure of cluster terms. For heterospin Cu(hfac)2L(R) complexes ("breathing crystals") with a "head-to-head" chain motif, a two-point approximation for a partition function of the Jahn-Teller Cu(+2) paramagnetic center (spin 1/2) is suggested. Theoretical results are compared with available experimental data on thermal spin-crossover-like transitions in the "breathing crystal" compounds. It is shown that the model developed is able to successfully describe both of the cases of smooth and abrupt (cooperative) spin transitions for chains of three-spin exchange clusters. Spin-crossover-like transitions of a new type with step-wise changes in a positive exchange integral are predicted.

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The Role of Binary and Many-Centre Molecular Interactions in Spin Crossover in the Solid State. Part IV. Ordering in Systems with Many-Body Interactions

Cited by 13 publications

References 24 publications

Influence of Sample Preparation, Temperature, Light, and Pressure on the Two-Step Spin Crossover Mononuclear Compound [Fe(bapbpy)(NCS)₂]

Influence of Sample Preparation, Temperature, Light, and Pressure on the Two-Step Spin Crossover Mononuclear Compound [Fe(bapbpy)(NCS)₂]

Cooperativity in Spin Crossover Systems. An Atomistic Perspective on the Devil’s Staircase

Cooperative spin-crossover-like transitions in the inhomogeneous chain of exchange clusters

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The Role of Binary and Many-Centre Molecular Interactions in Spin Crossover in the Solid State. Part IV. Ordering in Systems with Many-Body Interactions

Cited by 13 publications

References 24 publications

Influence of Sample Preparation, Temperature, Light, and Pressure on the Two-Step Spin Crossover Mononuclear Compound [Fe(bapbpy)(NCS)2]

Influence of Sample Preparation, Temperature, Light, and Pressure on the Two-Step Spin Crossover Mononuclear Compound [Fe(bapbpy)(NCS)2]

Cooperativity in Spin Crossover Systems. An Atomistic Perspective on the Devil’s Staircase

Cooperative spin-crossover-like transitions in the inhomogeneous chain of exchange clusters

Contact Info

Product

Resources

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Influence of Sample Preparation, Temperature, Light, and Pressure on the Two-Step Spin Crossover Mononuclear Compound [Fe(bapbpy)(NCS)₂]

Influence of Sample Preparation, Temperature, Light, and Pressure on the Two-Step Spin Crossover Mononuclear Compound [Fe(bapbpy)(NCS)₂]