An Fe II spin-crossover complex becomes increasingly cooperative with ageing

Gavin A. Craig, José Sánchez Costa, Olivier Roubeau, Simon J. Teat, Guillem Aromí

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Abstract

The polypyrazolyl ligand H4L, a functionalised derivative of 3-bpp [bpp = bis(pyrazol-3-yl)pyridine], has been used to synthesise an FeII spin-crossover (SCO) system [Fe(H4L)2](ClO4)2·2THF·H2O (1). A subsequent magnetic and structural study revealed that the compound undergoes an incomplete transition with a small hysteresis loop of 8 K and a large residual high spin (HS) fraction. This is consistent with single crystal diffraction results at 250 and 90 K, which show a slight modification of the crystal packing and Fe?N bond lengths. Ageing of the samples leads to more cooperative SCO behaviour, as evidenced by a concomitant increase in the width of the hysteresis loops (reaching up to 20 K) and a decrease in the residual HS fraction at low temperatures. These increases in the bistable domain of the sample, corroborated by measuring the changes in heat capacity through differential scanning calorimetry, are accompanied by a loss of crystallinity, which is attributed to solvent loss and the absorption of atmospheric water. Grinding an aged sample yields a narrower hysteresis loop at higher temperatures. Compound 1 was compared with two previously observed systems of the same family that exhibit different SCO behaviour, [Fe(H4L)2](ClO4)2·H2O·2(CH3)2CO (2) and [Fe(H4L)2](ClO4)2·2C3H7OH (3), by using Hirshfeld surface analysis to have a global view of the intermolecular interactions as enhanced by the functional groups of H4L.
Original languageEnglish
Pages (from-to)745-752
Number of pages8
JournalEuropean Journal of Inorganic Chemistry
Volume2013
Issue number5‐6
DOIs
Publication statusPublished - 18 Feb 2013

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Hysteresis loops
Aging of materials
Surface analysis
Bond length
Functional groups
Specific heat
Differential scanning calorimetry
Diffraction
Single crystals
Ligands
Derivatives
Temperature
Crystals
Water
perchlorate

Keywords

  • spin crossover
  • iron
  • magnetic properties
  • Intermolecular interactions
  • hirshfeld surfaces

Cite this

Craig, Gavin A. ; Costa, José Sánchez ; Roubeau, Olivier ; Teat, Simon J. ; Aromí, Guillem. / An Fe II spin-crossover complex becomes increasingly cooperative with ageing. In: European Journal of Inorganic Chemistry. 2013 ; Vol. 2013, No. 5‐6. pp. 745-752.
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An Fe II spin-crossover complex becomes increasingly cooperative with ageing. / Craig, Gavin A.; Costa, José Sánchez; Roubeau, Olivier; Teat, Simon J.; Aromí, Guillem.

In: European Journal of Inorganic Chemistry, Vol. 2013, No. 5‐6, 18.02.2013, p. 745-752.

Research output: Contribution to journalArticle

TY - JOUR

T1 - An Fe II spin-crossover complex becomes increasingly cooperative with ageing

AU - Craig, Gavin A.

AU - Costa, José Sánchez

AU - Roubeau, Olivier

AU - Teat, Simon J.

AU - Aromí, Guillem

PY - 2013/2/18

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N2 - The polypyrazolyl ligand H4L, a functionalised derivative of 3-bpp [bpp = bis(pyrazol-3-yl)pyridine], has been used to synthesise an FeII spin-crossover (SCO) system [Fe(H4L)2](ClO4)2·2THF·H2O (1). A subsequent magnetic and structural study revealed that the compound undergoes an incomplete transition with a small hysteresis loop of 8 K and a large residual high spin (HS) fraction. This is consistent with single crystal diffraction results at 250 and 90 K, which show a slight modification of the crystal packing and Fe?N bond lengths. Ageing of the samples leads to more cooperative SCO behaviour, as evidenced by a concomitant increase in the width of the hysteresis loops (reaching up to 20 K) and a decrease in the residual HS fraction at low temperatures. These increases in the bistable domain of the sample, corroborated by measuring the changes in heat capacity through differential scanning calorimetry, are accompanied by a loss of crystallinity, which is attributed to solvent loss and the absorption of atmospheric water. Grinding an aged sample yields a narrower hysteresis loop at higher temperatures. Compound 1 was compared with two previously observed systems of the same family that exhibit different SCO behaviour, [Fe(H4L)2](ClO4)2·H2O·2(CH3)2CO (2) and [Fe(H4L)2](ClO4)2·2C3H7OH (3), by using Hirshfeld surface analysis to have a global view of the intermolecular interactions as enhanced by the functional groups of H4L.

AB - The polypyrazolyl ligand H4L, a functionalised derivative of 3-bpp [bpp = bis(pyrazol-3-yl)pyridine], has been used to synthesise an FeII spin-crossover (SCO) system [Fe(H4L)2](ClO4)2·2THF·H2O (1). A subsequent magnetic and structural study revealed that the compound undergoes an incomplete transition with a small hysteresis loop of 8 K and a large residual high spin (HS) fraction. This is consistent with single crystal diffraction results at 250 and 90 K, which show a slight modification of the crystal packing and Fe?N bond lengths. Ageing of the samples leads to more cooperative SCO behaviour, as evidenced by a concomitant increase in the width of the hysteresis loops (reaching up to 20 K) and a decrease in the residual HS fraction at low temperatures. These increases in the bistable domain of the sample, corroborated by measuring the changes in heat capacity through differential scanning calorimetry, are accompanied by a loss of crystallinity, which is attributed to solvent loss and the absorption of atmospheric water. Grinding an aged sample yields a narrower hysteresis loop at higher temperatures. Compound 1 was compared with two previously observed systems of the same family that exhibit different SCO behaviour, [Fe(H4L)2](ClO4)2·H2O·2(CH3)2CO (2) and [Fe(H4L)2](ClO4)2·2C3H7OH (3), by using Hirshfeld surface analysis to have a global view of the intermolecular interactions as enhanced by the functional groups of H4L.

KW - spin crossover

KW - iron

KW - magnetic properties

KW - Intermolecular interactions

KW - hirshfeld surfaces

U2 - 10.1002/ejic.201201041

DO - 10.1002/ejic.201201041

M3 - Article

VL - 2013

SP - 745

EP - 752

JO - European Journal of Inorganic Chemistry

JF - European Journal of Inorganic Chemistry

SN - 1434-1948

IS - 5‐6

ER -