Coupled crystallographic order-disorder and spin state in a bistable molecule: multiple transition dynamics

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

Research output: Contribution to journalArticle

51 Citations (Scopus)

Abstract

Abstract A novel bispyrazolylpyridine ligand incorporating lateral phenol groups, H4L, has led to an FeII spin-crossover (SCO) complex, [Fe(H4L)2][ClO4]2H2O2(CH3)2CO (1), with an intricate network of intermolecular interactions. It exhibits a 40K wide hysteresis of magnetization as a result of the spin transition (with T0.5 of 133 and 173K) and features an unsymmetrical and very rich structure. The latter is a consequence of the coupling between the SCO and the crystallographic transformations. The high-spin state may also be thermally trapped, exhibiting a very large TTIESST (≈104K). The structure of 1 has been determined at various temperatures after submitting the crystal to different processes to recreate the key points of the hysteresis cycle and thermal trapping; 200K, cooled to 150K and trapped at 100K (high spin, HS), slowly cooled to 100K and warmed to 150K (low spin, LS). In the HS state, the system always exhibits disorder for some components (one ClO4 and two acetone molecules) whereas the LS phases show a relative ≈9% reduction in the FeN bond lengths and anisotropic contraction of the unit cell. Most importantly, in the LS state all the species are always found to be ordered. Therefore, the bistability of crystallographic order?disorder coupled to SCO is demonstrated here experimentally for the first time. The variation in the cell parameters in 1 also exhibits hysteresis. The structural and magnetic thermal variations in this compound are paralleled by changes in the heat capacity as measured by differential scanning calorimetry. Attempts to simulate the asymmetric SCO behaviour of 1 by using an Ising-like model underscore the paramount role of dynamics in the coupling between the SCO and the crystallographic transitions.
LanguageEnglish
Pages3120-3127
Number of pages8
JournalChemistry - A European Journal
Volume17
Issue number11
Early online date15 Feb 2011
DOIs
Publication statusPublished - 7 Mar 2011

Fingerprint

Order disorder transitions
Hysteresis
Molecules
Bond length
Acetone
Phenol
Phenols
Specific heat
Differential scanning calorimetry
Magnetization
Ligands
Crystals
Temperature
perchlorate
Hot Temperature

Keywords

  • bistability
  • hysteresis
  • iron
  • magnetic properties
  • order–disorder transitions
  • spin crossover

Cite this

Craig, Gavin A. ; Sánchez Costa, José ; Roubeau, Olivier ; Teat, Simon J. ; Aromí, Guillem. / Coupled crystallographic order-disorder and spin state in a bistable molecule : multiple transition dynamics. In: Chemistry - A European Journal. 2011 ; Vol. 17, No. 11. pp. 3120-3127.
@article{d73c743fbcfe4cb8a00678488c9b2b42,
title = "Coupled crystallographic order-disorder and spin state in a bistable molecule: multiple transition dynamics",
abstract = "Abstract A novel bispyrazolylpyridine ligand incorporating lateral phenol groups, H4L, has led to an FeII spin-crossover (SCO) complex, [Fe(H4L)2][ClO4]2H2O2(CH3)2CO (1), with an intricate network of intermolecular interactions. It exhibits a 40K wide hysteresis of magnetization as a result of the spin transition (with T0.5 of 133 and 173K) and features an unsymmetrical and very rich structure. The latter is a consequence of the coupling between the SCO and the crystallographic transformations. The high-spin state may also be thermally trapped, exhibiting a very large TTIESST (≈104K). The structure of 1 has been determined at various temperatures after submitting the crystal to different processes to recreate the key points of the hysteresis cycle and thermal trapping; 200K, cooled to 150K and trapped at 100K (high spin, HS), slowly cooled to 100K and warmed to 150K (low spin, LS). In the HS state, the system always exhibits disorder for some components (one ClO4 and two acetone molecules) whereas the LS phases show a relative ≈9{\%} reduction in the FeN bond lengths and anisotropic contraction of the unit cell. Most importantly, in the LS state all the species are always found to be ordered. Therefore, the bistability of crystallographic order?disorder coupled to SCO is demonstrated here experimentally for the first time. The variation in the cell parameters in 1 also exhibits hysteresis. The structural and magnetic thermal variations in this compound are paralleled by changes in the heat capacity as measured by differential scanning calorimetry. Attempts to simulate the asymmetric SCO behaviour of 1 by using an Ising-like model underscore the paramount role of dynamics in the coupling between the SCO and the crystallographic transitions.",
keywords = "bistability, hysteresis, iron, magnetic properties, order–disorder transitions, spin crossover",
author = "Craig, {Gavin A.} and Jos{\'e} S{\'a}nchez Costa and Olivier Roubeau and Teat, {Simon J.} and Guillem Arom{\'i}",
year = "2011",
month = "3",
day = "7",
doi = "10.1002/chem.201003197",
language = "English",
volume = "17",
pages = "3120--3127",
journal = "Chemistry - A European Journal",
issn = "0947-6539",
number = "11",

}

Coupled crystallographic order-disorder and spin state in a bistable molecule : multiple transition dynamics. / Craig, Gavin A.; Sánchez Costa, José; Roubeau, Olivier; Teat, Simon J.; Aromí, Guillem.

In: Chemistry - A European Journal, Vol. 17, No. 11, 07.03.2011, p. 3120-3127.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Coupled crystallographic order-disorder and spin state in a bistable molecule

T2 - Chemistry - A European Journal

AU - Craig, Gavin A.

AU - Sánchez Costa, José

AU - Roubeau, Olivier

AU - Teat, Simon J.

AU - Aromí, Guillem

PY - 2011/3/7

Y1 - 2011/3/7

N2 - Abstract A novel bispyrazolylpyridine ligand incorporating lateral phenol groups, H4L, has led to an FeII spin-crossover (SCO) complex, [Fe(H4L)2][ClO4]2H2O2(CH3)2CO (1), with an intricate network of intermolecular interactions. It exhibits a 40K wide hysteresis of magnetization as a result of the spin transition (with T0.5 of 133 and 173K) and features an unsymmetrical and very rich structure. The latter is a consequence of the coupling between the SCO and the crystallographic transformations. The high-spin state may also be thermally trapped, exhibiting a very large TTIESST (≈104K). The structure of 1 has been determined at various temperatures after submitting the crystal to different processes to recreate the key points of the hysteresis cycle and thermal trapping; 200K, cooled to 150K and trapped at 100K (high spin, HS), slowly cooled to 100K and warmed to 150K (low spin, LS). In the HS state, the system always exhibits disorder for some components (one ClO4 and two acetone molecules) whereas the LS phases show a relative ≈9% reduction in the FeN bond lengths and anisotropic contraction of the unit cell. Most importantly, in the LS state all the species are always found to be ordered. Therefore, the bistability of crystallographic order?disorder coupled to SCO is demonstrated here experimentally for the first time. The variation in the cell parameters in 1 also exhibits hysteresis. The structural and magnetic thermal variations in this compound are paralleled by changes in the heat capacity as measured by differential scanning calorimetry. Attempts to simulate the asymmetric SCO behaviour of 1 by using an Ising-like model underscore the paramount role of dynamics in the coupling between the SCO and the crystallographic transitions.

AB - Abstract A novel bispyrazolylpyridine ligand incorporating lateral phenol groups, H4L, has led to an FeII spin-crossover (SCO) complex, [Fe(H4L)2][ClO4]2H2O2(CH3)2CO (1), with an intricate network of intermolecular interactions. It exhibits a 40K wide hysteresis of magnetization as a result of the spin transition (with T0.5 of 133 and 173K) and features an unsymmetrical and very rich structure. The latter is a consequence of the coupling between the SCO and the crystallographic transformations. The high-spin state may also be thermally trapped, exhibiting a very large TTIESST (≈104K). The structure of 1 has been determined at various temperatures after submitting the crystal to different processes to recreate the key points of the hysteresis cycle and thermal trapping; 200K, cooled to 150K and trapped at 100K (high spin, HS), slowly cooled to 100K and warmed to 150K (low spin, LS). In the HS state, the system always exhibits disorder for some components (one ClO4 and two acetone molecules) whereas the LS phases show a relative ≈9% reduction in the FeN bond lengths and anisotropic contraction of the unit cell. Most importantly, in the LS state all the species are always found to be ordered. Therefore, the bistability of crystallographic order?disorder coupled to SCO is demonstrated here experimentally for the first time. The variation in the cell parameters in 1 also exhibits hysteresis. The structural and magnetic thermal variations in this compound are paralleled by changes in the heat capacity as measured by differential scanning calorimetry. Attempts to simulate the asymmetric SCO behaviour of 1 by using an Ising-like model underscore the paramount role of dynamics in the coupling between the SCO and the crystallographic transitions.

KW - bistability

KW - hysteresis

KW - iron

KW - magnetic properties

KW - order–disorder transitions

KW - spin crossover

U2 - 10.1002/chem.201003197

DO - 10.1002/chem.201003197

M3 - Article

VL - 17

SP - 3120

EP - 3127

JO - Chemistry - A European Journal

JF - Chemistry - A European Journal

SN - 0947-6539

IS - 11

ER -