Synergy between polymorphism, pressure, spin-crossover and temperature in [Fe(PM-BiA)2(NCS)2]: a neutron powder diffraction investigation

Legrand, Vincent; Péchev, Stanislav; Létard, Jean‐François; Guionneau, Philippe

doi:10.1039/c3cp51444g

Cited by 19 publications

(23 citation statements)

References 53 publications

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“…and Raman) of the molecule in its two spin states by molecular simulation (Figure 8). Particularly we found, in agreement with the experiment [30], that the Fe–N 6 octahedron is more distorted in the high-spin state than in the low-spin one, as illustrated by the distance changes: Δ d HS = 0.21 Å much larger than Δ d LS = 0.03 Å as well as for the angles extremes: Δθ HS = 26.4° > Δθ LS = 13.7°.…”

Section: Resultssupporting

confidence: 91%

“…The latter is mainly explained by considerations on the crystal packing. More recently, preliminary experimental investigation of the (P, T) phase diagram by means of neutron diffraction have revealed that applying pressure to the orthorhombic polymorph induces a structural transition to the monoclinic polymorph [30] leading to an intricate spin and structural phases diagram. As it is further shown below, molecular simulation has been used to determine the full (P, T) phase diagram, overcoming the high experimental difficulty to obtain reliable high pressure crystal structure at variable (low) temperature as well as its high cost [31].…”

Section: Resultsmentioning

confidence: 99%

“…The domains delimitated by straight curves generate two triple points. Experimental points from [30] are presented for comparison (LS (I): filled red squares; HS (I): filled red down triangles; LS (II): empty red square; HS (II): empty red up triangles).…”

Section: Resultsmentioning

confidence: 99%

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Multiscale Experimental and Theoretical Investigations of Spin Crossover FeII Complexes: Examples of [Fe(phen)2(NCS)2] and [Fe(PM-BiA)2(NCS)2]

Matar

Guionneau

Chastanet

2015

IJMS

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For spin crossover (SCO) complexes, computation results are reported and confirmed with experiments at multiscale levels of the isolated molecule and extended solid on the one hand and theory on the other hand. The SCO phenomenon which characterizes organometallics based on divalent iron in an octahedral FeN6-like environment with high spin (HS) and low spin (LS) states involves the LS/HS switching at the cost of small energies provided by temperature, pressure or light, the latter connected with Light-Induced Excited Spin-State Trapping (LIESST) process. Characteristic infra red (IR) and Raman vibration frequencies are computed within density functional theory (DFT) framework. In [Fe(phen)2(NCS)2] a connection of selected frequencies is established with an ultra-fast light-induced LS → HS photoswitching mechanism. In the extended solid, density of state DOS and electron localization function (ELF) are established for both LS and HS forms, leading to characterizion of the compound as an insulator in both spin states with larger gaps for LS configuration, while keeping molecular features in the solid. In [Fe(PM-BiA)2(NCS)2], by combining DFT and classical molecular dynamics, the properties and the domains of existence of the different phases are obtained by expressing the potential energy surfaces in a short range potential for Fe–N interactions. Applying such Fe–N potentials inserted in a classical force field and carrying out molecular dynamics (MD) in so-called “semi-classical MD” calculations, lead to the relative energies of HS/LS configurations of the crystal and to the assessment of the experimental (P, T) phase diagram.

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Section: Resultssupporting

confidence: 91%

Section: Resultsmentioning

confidence: 99%

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Multiscale Experimental and Theoretical Investigations of Spin Crossover FeII Complexes: Examples of [Fe(phen)2(NCS)2] and [Fe(PM-BiA)2(NCS)2]

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Guionneau

Chastanet

2015

IJMS

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“…Some compounds of the same series have shown a SCO at room temperature but for pressure higher than 700 MPa [46,47]. Let us recall that single crystals of [Fe(PM-PEA) 2 (NCS) 2 ] are well-known from variable temperature measurements [43] to crystallize in the monoclinic system in the HS state and in the orthorhombic system in the LS state; the unit-cell volume variation due to the thermal SCO being of the order of 3%.…”

Section: Sco At High-pressurementioning

confidence: 99%

Effects of Internal and External Pressure on the [Fe(PM-PEA)2(NCS)2] Spin-Crossover Compound (with PM-PEA = N-(2′-pyridylmethylene)-4-(phenylethynyl)aniline)

et al. 2016

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Abstract:The spin-crossover properties of the strongly cooperative compound [Fe(PM-PEA) 2 (NCS) 2 ] (with PM-PEA = N-(2 1 -pyridylmethylene)-4-(phenylethynyl)aniline) have been investigated under external in situ pressure, external ex situ pressure and internal pressure. In situ single-crystal X-ray diffraction investigations under pressure indicate a Spin-Crossover (SCO) at about 400 MPa and room temperature. Interestingly, application of ex situ pressure induces the irreversible enlargement of the hysteresis width, almost independently from the pressure value. Elsewhere, the internal pressure effects are examined through the magnetic and photomagnetic investigations on powders of the solid-solutions based on the Mn ion, [Fe x Mn 1´x (PM-PEA) 2 (NCS) 2 ]. Growing the Mn ratio increases the internal pressure, allowing to control the hysteresis width and the paramagnetic residue but also to enhance the efficiency of the photo-induced SCO. The comparison of the quenching and light-induced behaviors reveals a complex phase-diagram governed by internal pressure, temperature and light.

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“…21 The pressure-induced LS structure has only been reported in four of those studies, all concerning iron(II). 10,19 This is despite interest in probing the similarities and differences between the structures of the pressure-induced and temperature-induced LS states, 22 especially for metal ions which undergo anisotropic M-L changes (Jahn Teller), such as cobalt(II). Rather than full structure determinations, the effect of pressure is more commonly followed crystallographically by monitoring changes to the unit cell constants.…”

Section: Introductionmentioning

confidence: 99%

Pressure induced separation of phase-transition-triggered-abrupt vs. gradual components of spin crossover

et al. 2015

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The application of pressure on [Co(II)(dpzca)2], which at ambient pressure undergoes abrupt spin crossover (SCO) with thermal hysteresis, gives unique insights into SCO. It reversibly separates the crystallographic phase transition (I41/a↔P21/c) and associated abrupt SCO from the underlying gradual SCO, as shown by detailed room temperature (RT) X-ray crystallography and temperature dependent magnetic susceptibility studies, both under a range of 10 different pressures. The pressure effects are shown to be reversible. The crystal structure of the pressure-induced low-spin state is determined at RT at 0.42(2) and 1.78(9) GPa. At the highest pressure [1.78(9) GPa] the Co-N bond lengths are consistent with the complex being fully LS, and the conjugated terdentate ligands are significantly distorted out of plane. The abrupt SCO event can be shifted up to RT by application of a hydrostatic pressure of ∼0.4 GPa. These magnetic susceptibility (vs. temperature) and X-ray crystallography (at RT) studies, under a range of pressures, show that the SCO can be tuned over a wide range of temperature and pressure space, including RT SCO.

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Synergy between polymorphism, pressure, spin-crossover and temperature in [Fe(PM-BiA)2(NCS)2]: a neutron powder diffraction investigation

Cited by 19 publications

References 53 publications

Multiscale Experimental and Theoretical Investigations of Spin Crossover FeII Complexes: Examples of [Fe(phen)2(NCS)2] and [Fe(PM-BiA)2(NCS)2]

Multiscale Experimental and Theoretical Investigations of Spin Crossover FeII Complexes: Examples of [Fe(phen)2(NCS)2] and [Fe(PM-BiA)2(NCS)2]

Effects of Internal and External Pressure on the [Fe(PM-PEA)2(NCS)2] Spin-Crossover Compound (with PM-PEA = N-(2′-pyridylmethylene)-4-(phenylethynyl)aniline)

Pressure induced separation of phase-transition-triggered-abrupt vs. gradual components of spin crossover

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