A probe of steric ligand substituent effects on the spin crossover of Fe(<scp>ii</scp>) complexes

Bartual‐Murgui, Carlos; Vela, Sergi; Darawsheh, Mohanad; Diego, Rosa; Teat, Simon J.; Roubeau, Olivier; Aromı́, Guillem

doi:10.1039/c7qi00347a

Cited by 37 publications

(55 citation statements)

References 61 publications

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“…15,27,28 Similarly, T½(solution) for [Fe (1,3-bpp)2] 2+ has been measured as 254 K in acetone 15 or 262 K in MeOH. 29 We employed the lower T½(solution) values in this analysis, which reflects the hydrophobic lattices in the anhydrous crystals in the derivatives, which have no hydrogen bond donors in their heterocyclic ligand framework. 17 Table 1.…”

Section: Resultsmentioning

confidence: 99%

Relationship between the Molecular Structure and Switching Temperature in a Library of Spin-Crossover Molecular Materials

et al. 2019

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Structure:function relationships are surveyed relating the spin-crossover (SCO) midpoint temperature (T½) in the solid state, for 43 members of the iron(II)/dipyrazolylpyridine family of SCO compounds. The difference between T½ in the solid state and in solution [T(latt)] is proposed as a measure of the lattice contribution to the transition temperature. Negative linear correlations between SCO temperature and the magnitude of the rearrangement of the coordination sphere during SCO are evident among isostructural or near-isostructural subsets of compounds; that is, a larger change in molecular structure during SCO stabilizes the high-spin state of a material. Improved correlations are often obtained when T(latt), rather than the raw T½ value, is considered as the measure of SCO temperature. Different lattice types show different tendencies to stabilize the high-spin or low-spin state of the molecules containing them, which correlates with the structural changes that most influence T(latt) in each case. These relationships are mostly unaffected by the SCO cooperativity in the compounds, or by the involvement of any crystallographic phase changes. One or two materials within each subset are outliers in some or all of these correlations however which, in some cases, can be attributed to small differences in their ligand geometry or unusual phase behavior during SCO. A reinvestigation of the structural chemistry of [Fe(3-bpp)2][NCS]2•nH2O (3-bpp = di{1H-pyrazol-3-yl}pyridine; n = 0 or 2), undertaken as part of this study, is also presented. .

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Section: Resultsmentioning

confidence: 99%

Relationship between the Molecular Structure and Switching Temperature in a Library of Spin-Crossover Molecular Materials

et al. 2019

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“…The absence of all of these effects in the solution enables the effect of ligand modifications on the ligand field strength imposed on the Fe(II) centres to be clearly seen. 39,74,75 Hence, the spin state of the five new dinuclear helicates 1-5 is monitored in acetonitrile solution at variable temperatures using both the 1 H NMR Evans method and by UV-vis spectroscopy (discussed in this and the following sections).…”

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confidence: 99%

Correlations between ligand field Δ_o, spin crossover T_1/2 and redox potential E_pa in a family of five dinuclear helicates

Singh

Brooker

2021

Chem. Sci.

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“…S15), resulting in a number, n, of interacting molecules per domain of 17.0, characteristic of a medium to high cooperative character of the SCO process (values of n close to unity are expected for gradual SCO while values above 20 are found for strongly cooperative systems). [43][44] DFT energy calculations of the solid-state conversions…”

Section: Thermal Signatures Of the Successive Phase Transitionsmentioning

confidence: 99%

A Spin-Crossover Molecular Material Describing Four Distinct Thermal Pathways

et al. 2018

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Spin-crossover (SCO) molecular solids are valued switchable materials for their common abrupt and reversible thermal transitions, large thermal hysteresis, or guest-dependent effects. These properties usually involve crystallographic transitions coupled to the SCO events. These phenomena are of great value for the understanding of solid-state transformations and also for exploiting them. We present here a lattice of the complex [FeL(bbp)](ClO) (1; L and bbp are tris-imine ligands) featuring an unprecedented rich succession of SCO and crystallographic phase transformations. Magnetometry measurements unveil a thermally irreversible sequence of spin conversions that delineate four different thermal pathways. All of these are single-crystal-to-single-crystal processes and can thus be monitored by single crystal X-ray diffraction using one unique specimen. Fresh crystals of 1 contain one molecule of acetone per Fe center (1·ac) that abandons the lattice upon warming at the same time that a SCO from an ordered mixed spin state (1:1 high spin/low spin; HS/LS) to a fully HS state, 1, occurs. This crystallographic phase, accessed through a template effect by the solvent, converts into another one, 1, upon cooling, as triggered by a HS to LS SCO. Warming of 1 induces a new SCO (LS to ordered HS/LS) coupled to another crystallographic phase transition, 1 → 1. The fully HS state of 1 can not be reached before decomposition of the compound. Instead, this phase cycles between the HS/LS and the LS states through superimposable pathways, different from that of the prerequired 1 → 1 phase change. Analysis of the thermal variation of the free energy, G, through density functional theory methods provides trends in agreement with the observation of these transformations and clarifies the possible metastable nature of the various phases identified. This unique behavior allows the access to four different magnetic responses depending on the thermal history of the sample, within a given range of temperatures near the ambient conditions.

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A probe of steric ligand substituent effects on the spin crossover of Fe(ii) complexes

Abstract: Ligand substituents modulate the SCO temperature of Fe(ii) complexes through intramolecular non-covalent interactions.

Cited by 37 publications

References 61 publications

Relationship between the Molecular Structure and Switching Temperature in a Library of Spin-Crossover Molecular Materials

Relationship between the Molecular Structure and Switching Temperature in a Library of Spin-Crossover Molecular Materials

Correlations between ligand field Δ_o, spin crossover T_1/2 and redox potential E_pa in a family of five dinuclear helicates

A Spin-Crossover Molecular Material Describing Four Distinct Thermal Pathways

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A probe of steric ligand substituent effects on the spin crossover of Fe(ii) complexes

Abstract: Ligand substituents modulate the SCO temperature of Fe(ii) complexes through intramolecular non-covalent interactions.

Cited by 37 publications

References 61 publications

Relationship between the Molecular Structure and Switching Temperature in a Library of Spin-Crossover Molecular Materials

Relationship between the Molecular Structure and Switching Temperature in a Library of Spin-Crossover Molecular Materials

Correlations between ligand field Δo, spin crossover T1/2 and redox potential Epa in a family of five dinuclear helicates

A Spin-Crossover Molecular Material Describing Four Distinct Thermal Pathways

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Correlations between ligand field Δ_o, spin crossover T_1/2 and redox potential E_pa in a family of five dinuclear helicates