Symmetry Breaking in Iron(II) Spin-Crossover Molecular Crystals

Ortega-Villar, Norma; Muñoz, M. Carmen; Real, José Antonio

doi:10.3390/magnetochemistry2010016

Cited by 88 publications

(89 citation statements)

References 82 publications

(87 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Each of the three possible states may be reached and maintained for a large temperature range ([HS–HS] over more than 400 K for 1 b and 2 b ; [LS–HS] over more than 200 K for 1 ; [LS–LS] over more than 100 K for 1 a ). While the versatility of this system is remarkable, the occurrence of [HS–LS] situations is not new . It has been identified in several instances before, sometimes involving helicates or several other discrete dinuclear complexes .…”

Section: Resultsmentioning

confidence: 94%

Guest‐, Light‐ and Thermally‐Modulated Spin Crossover in [Fe^II₂] Supramolecular Helicates

Darawsheh

Barrios

Roubeau

et al. 2016

Chemistry A European J

View full text Add to dashboard Cite

A new bis(pyrazolylpyridine) ligand (H2 L) has been prepared to form functional [Fe2 (H2 L)3 ](4+) metallohelicates. Changes to the synthesis yield six derivatives, X@[Fe2 (H2 L)3 ]X(PF6 )2 ⋅xCH3 OH (1, x=5.7 and X=Cl; 2, x=4 and X=Br), X@[Fe2 (H2 L)3 ]X(PF6 )2 ⋅yCH3 OH⋅H2 O (1 a, y=3 and X=Cl; 2 a, y=1 and X=Br) and X@[Fe2 (H2 L)3 ](I3 )2 ⋅3 Et2 O (1 b, X=Cl; 2 b, X=Br). Their structure and functional properties are described in detail by single-crystal X-ray diffraction experiments at several temperatures. Helicates 1 a and 2 a are obtained from 1 and 2, respectively, by a single-crystal-to-single-crystal mechanism. The three possible magnetic states, [LS-LS], [LS-HS], and [HS-HS] can be accessed over large temperature ranges as a result of the structural nonequivalence of the Fe(II) centers. The nature of the guest (Cl(-) vs. Br(-) ) shifts the spin crossover (SCO) temperature by roughly 40 K. Also, metastable [LS-HS] or [HS-HS] states are generated through irradiation. All helicates (X@[Fe2 (H2 L)3 ])(3+) persist in solution.

show abstract

Section: Resultsmentioning

confidence: 94%

Guest‐, Light‐ and Thermally‐Modulated Spin Crossover in [Fe^II₂] Supramolecular Helicates

Darawsheh

Barrios

Roubeau

et al. 2016

Chemistry A European J

View full text Add to dashboard Cite

show abstract

“…Although, crystallographic symmetry breaking giving intermediate steps was previously observed for the mononuclear SCO complexes [Fe 27-29 So far, a relatively small number of complete two-step or incomplete (only one step of two expected) SCO events with symmetry breaking have been observed in mononuclear, [30][31][32][33][34][35][36][37][38][39] polynuclear, [40][41][42][43] and polymeric [44][45][46][47][48][49][50][51][52][53] Fe II SCO complexes, and reviewed recently. 54,55 This phenomenology has also been described for a reduced number of Fe III , [56][57][58][59][60] Co II 61 and Mn III 62 complexes. Most of these examples exhibit spontaneous generation of a stable state characterized by a plateau at HS molar fraction HS ≈ 1/2 and an ordered distribution of the HS and LS centers directly observed from single crystal X-ray analysis.…”

Section: Introductionmentioning

confidence: 78%

Competing Phases Involving Spin-State and Ligand Structural Orderings in a Multistable Two-Dimensional Spin Crossover Coordination Polymer

Trzop

Valverde‐Muñoz

Piñeiro‐López

et al. 2017

Crystal Growth & Design

View full text Add to dashboard Cite

Competition between spin-crossover (SCO) and structural ligand ordering is identified as responsible for multi-stability and generation of six different phases in a rigid two-dimensional (2D) coordination polymer formulated {Fe Furthermore, two additional phases are generated at low temperature. One, LS2 (HS = 0, phase 5), is due to spontaneous symmetry breaking of the LS1 state below 85 K. The other, results from irradiating the low-temperature LS2 phase at 15 K with red light to photo-generate a HS phase of low symmetry (HS*) (HS = 1, phase 6). Detailed structural studies of the six phases unravel the pivotal role played by the internal dihedral angle of the 4,4'-bipy ligands in the microscopic mechanism responsible for multistability and multi-step behavior in 1.Competing phases involving spin-state and ligand structural orderings in a multistable two-dimensional spin crossover coordination polymer INTRODUCTIONIron(II) spin crossover (SCO) complexes are switchable molecular materials that respond to environmental stimuli (T, P, light, analytes) through changes in magnetic, optical, electrical and mechanical properties associated with the high-(HS) and low-spin (LS) states of the SCO centre. The intrinsic on-off nature of the LSHS switch has attracted much interest not only because it constitutes an excellent platform for investigating models of thermal-, pressure and photoinduced phase transitions 1-13 in molecular materials but also because many expectancies have been created regarding to the conception of SCO-based devices, i.e. sensors, actuators and memories. [14][15][16][17][18][19][20][21][22][23][24] This has led to an impressive growth of the SCO field in the last decade as a result of cross-seeding interaction between different areas of research ranging from coordination chemistry, materials science and solid state physics.A pivotal current aspect that transcends the SCO research is the understanding of the elusive principles underlying cooperativity in multi-step spin transitions in the solid-state.Steps may occur when elastic forces favor competition between spatial periodicities of structural inequivalent SCO centers. For example, the presence of crystallographically distinct sites with different ligand field strengths. However, even if there is a unique SCO center in the crystal, inequivalence between SCO centers may spontaneously originate as a consequence of crystallographic symmetry breaking. Although, crystallographic symmetry breaking giving intermediate steps was previously observed for the mononuclear SCO complexes [Fe

show abstract

“…1−4 Although a large number of such materials have been developed, leading to a good understanding of the intramolecular properties (choice of metal ion, donor atom, sterics, etc.) 1,2,5−11 that affect spin transitions in discrete complexes, the results of cooperative intramolecular effects (leading to hysteresis, sharp transitions, etc.) 1,2,5,12 are still not readily predictable.…”

Section: Introductionmentioning

confidence: 99%

“…1,2,5−11 that affect spin transitions in discrete complexes, the results of cooperative intramolecular effects (leading to hysteresis, sharp transitions, etc.) 1,2,5,12 are still not readily predictable. This is particularly the case for supramolecular effects involving weak noncovalent interactions and/or crystal packing.…”

Section: Introductionmentioning

confidence: 99%

Spin-State Patterning in an Iron(II) Tripodal Spin-Crossover Complex

Neville

Craze

et al. 2017

ACS Omega

View full text Add to dashboard Cite

A mononuclear iron(II) complex that displays a gradual two-step spin-crossover (SCO) transition is reported. The intermediate plateau (IP) occurs between HS 0.40 LS 0.60 and HS 0.30 LS 0.70 (HS = high spin; LS = low spin) ratios over the region of ca. 190–170 K. A phase change occurs at the IP, breaking the symmetry, resulting in six independent SCO sites compared to one at the 100% HS and LS plateau regions, respectively. Variable-temperature X-ray photoelectron spectroscopy shows that the SCO behavior is completely reversible among the HS, IP, and LS regions. The results both confirm and extend the related results for the above system described by Halcrow et al. ( Gradual Thermal Spin-Crossover Mediated By a Reentrant Z ′ = 1 → Z ′ = 6 → Z ′ = 1 Phase Transition Kulmaczewski R. Cespedes O. Halcrow M. A. Kulmaczewski R. Cespedes O. Halcrow M. A. 28244751 Inorg. Chem 2017 56 3144 3148 ) in a recent report.

show abstract

Symmetry Breaking in Iron(II) Spin-Crossover Molecular Crystals

Cited by 88 publications

References 82 publications

Guest‐, Light‐ and Thermally‐Modulated Spin Crossover in [Fe^II₂] Supramolecular Helicates

Guest‐, Light‐ and Thermally‐Modulated Spin Crossover in [Fe^II₂] Supramolecular Helicates

Competing Phases Involving Spin-State and Ligand Structural Orderings in a Multistable Two-Dimensional Spin Crossover Coordination Polymer

Spin-State Patterning in an Iron(II) Tripodal Spin-Crossover Complex

Contact Info

Product

Resources

About

Symmetry Breaking in Iron(II) Spin-Crossover Molecular Crystals

Cited by 88 publications

References 82 publications

Guest‐, Light‐ and Thermally‐Modulated Spin Crossover in [FeII2] Supramolecular Helicates

Guest‐, Light‐ and Thermally‐Modulated Spin Crossover in [FeII2] Supramolecular Helicates

Competing Phases Involving Spin-State and Ligand Structural Orderings in a Multistable Two-Dimensional Spin Crossover Coordination Polymer

Spin-State Patterning in an Iron(II) Tripodal Spin-Crossover Complex

Contact Info

Product

Resources

About

Guest‐, Light‐ and Thermally‐Modulated Spin Crossover in [Fe^II₂] Supramolecular Helicates

Guest‐, Light‐ and Thermally‐Modulated Spin Crossover in [Fe^II₂] Supramolecular Helicates