The nature of spin-state transitions in solid complexes of iron(II) and the interpretation of some associated phenomena

König, E.; Ritter, G.; Kulshreshtha, S. K.

doi:10.1021/cr00067a003

Cited by 362 publications

(147 citation statements)

References 35 publications

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“…However for a sample containing crystals with large sizes, the hysteresis loop observed is the sum of hysteresis loops which correspond to different transition temperatures and which have different widths. We think that this sum should be done as it is proposed in the Figure 4 of the article of König et al [14] From the previous results, we also deduce that the width, in the plane (n HS ,T), of the hysteresis loop observed on a sample decreases when the sizes of the crystals contained in the sample decrease. Moreover, the hysteresis loop calculated for a macroscopic crystal, given a certain size and shape, cannot be compared to that observed on a sample containing macroscopic crystals.…”

Section: Resultssupporting

confidence: 53%

Molecules with Two Electronic Energy Levels: Study of Nanoparticles in the Atom‐Phonon Coupling Model Including a Surface Effect

et al. 2018

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Abstract:We discuss a two-dimensional model that leads to results which reproduce, at least qualitatively, some of the experimentally observed features of spin-conversion compounds. The molecules of these compounds have two electronic energy levels separated by Δ. The values of the elastic constants of the springs contained in the molecules are lower in the upper level. Consequently, the phonon branches of the crystal depend on the electronic states of the molecules. The fundamental level is a low spin (LS) state and the excited one is a high spin (HS) state. We study the thermal variation of the high spin fraction, i.e., the fraction of molecules in the (HS) level by using a model

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Section: Resultssupporting

confidence: 53%

Molecules with Two Electronic Energy Levels: Study of Nanoparticles in the Atom‐Phonon Coupling Model Including a Surface Effect

et al. 2018

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“…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][2][3][4][5][6][7][8][9][10][11][12][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.…”

Section: Introductionmentioning

confidence: 99%

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

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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

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“…[1,2] A variety of iron(II) compounds are known to show a transition from the highspin state [HS, S ϭ 2, 5 T 2g (O h )] to the low-spin state [LS, S ϭ 0, 1 A 1g (O h )] on cooling. [2Ϫ4] Iron(II) compounds incorporating substituted 1,2,4-triazole ligands have been found to undergo spin transition.…”

Section: Introductionmentioning

confidence: 99%

Synthesis, Structure, and Magnetic Properties of a Tris[3-(2-pyridyl)-1,2,4-triazole]iron(II) Spin-Crossover Complex

Stassen

Vos

Koningsbruggen

et al. 2000

Eur. J. Inorg. Chem.

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The synthesis and characterization of tris[3‐(pyridin‐2‐yl)‐1,2,4‐triazole]iron(II) bis(tetrafluoroborate), obtained from the reaction of 3‐(pyridin‐2‐yl)‐1,2,4‐triazole (Hpt) and hexaaquairon(II) tetrafluoroborate, [Fe(H2O)6](BF4)2, is described, together with its crystal structures at two temperatures. X‐ray crystallographic parameters are as follows: [Fe(Hpt)3](BF4)2·nH2O (n ≈︁ 2) at 250 K: orthorhombic space group Pbam, a = 15.8068(18) Å, b = 17.2800(14) Å, c = 21.215(2) Å, V = 5794.7(10) Å3, and Z = 8. [Fe(Hpt)3](BF4)2·nH2O (n ≈︁ 2) at 95 K: orthorhombic space group Pbam, a = 15.7080(12) Å, b = 17.1023(16) Å, c = 21.006(2) Å, V = 5643.1(9) Å3, and Z = 8. The FeII ions are (at both temperatures) octahedrally surrounded in a mer‐configuration. The complex has been subjected to both 57Fe Mössbauer spectroscopy and magnetic susceptibility measurements. The 57Fe Mössbauer spectrum shows the presence of two different iron(II) sites. The high‐spin fraction vs. T curve of the crossover, obtained by SQUID measurements, is gradual and without hysteresis, with T1/2 = 135 K.

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The nature of spin-state transitions in solid complexes of iron(II) and the interpretation of some associated phenomena

Cited by 362 publications

References 35 publications

Molecules with Two Electronic Energy Levels: Study of Nanoparticles in the Atom‐Phonon Coupling Model Including a Surface Effect

Molecules with Two Electronic Energy Levels: Study of Nanoparticles in the Atom‐Phonon Coupling Model Including a Surface Effect

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

Synthesis, Structure, and Magnetic Properties of a Tris[3-(2-pyridyl)-1,2,4-triazole]iron(II) Spin-Crossover Complex

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