Slow magnetic relaxation in Fe(<scp>ii</scp>)<i>m</i>-terphenyl complexes

Valentine, Andrew J. S.; Geer, Ana M.; Blundell, Toby J.; Tovey, Will; Cliffe, Matthew J.; Davies, E. Stephen; Argent, Stephen P.; Lewis, William; McMaster, Jonathan; Taylor, Laurence J.; Reta, Daniel; Kays, Deborah L.

doi:10.1039/d2dt03531f

Cited by 4 publications

(3 citation statements)

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“…To probe the existence of slow relaxation of magnetization in the complex, AC measurements at zero and applied DC magnetic fields were performed at 1.8 K. Unfortunately, no out-of-phase susceptibility peaks ( χ ′′) were observed either at zero or applied DC fields (Fig. S26†), indicating that complex 2a is not a single-molecule magnet (SMM) at and above 1.8 K. This result is not surprising considering the fact that iron( ii )-based SMMs are not frequently observed 45 due to efficient quantum tunnelling of magnetization facilitating fast under barrier magnetization relaxation.…”

Section: Resultsmentioning

confidence: 90%

“…Unfortunately, no out-of-phase susceptibility peaks (χ") were observed either at zero or applied DC fields (Figure S26), indicating that complex 2a is not a single-molecule magnet (SMM) at and above 1.8 K. This result is not surprising considering the fact that iron(II)-based SMMs are not frequently observed 45 In addition to the magnetometry measurements, 57 Fe Mössbauer spectroscopy measurements were performed on 1•CH 3 CN to obtain the spin state composition at different temperatures.…”

Section: Dalton Transactions Accepted Manuscriptmentioning

confidence: 94%

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Lattice solvent- and substituent-dependent spin-crossover in isomeric iron(ii) complexes

Kuppusamy,

Mizuno,

Kämmerer

et al. 2024

Dalton Trans.

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Section: Resultsmentioning

confidence: 90%

Section: Dalton Transactions Accepted Manuscriptmentioning

confidence: 94%

Lattice solvent- and substituent-dependent spin-crossover in isomeric iron(ii) complexes

Kuppusamy,

Mizuno,

Kämmerer

et al. 2024

Dalton Trans.

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show abstract

“…Unfortunately, no out-of-phase susceptibility peaks (χ") were observed either at zero or applied DC fields (Figure S18), indicating that complex 2 is not an single-molecule magnet (SMM) at and above 1.8 K. This result is not surprising considering the fact that iron(II)-based SMMs are not frequently observed 42 due to efficient quantum tunnelling of magnetization facilitating fast under barrier magnetization relaxation. 57 Fe Mössbauer spectroscopic studies of 1•CH3CN…”

Section: Spin-state Switching Characteristics Of 1•ch3cn Andmentioning

confidence: 96%

Substituent-dependent spin-state switching in isomeric iron(II) complexes: from bi-stable spin-state switching with T1/2 centred at room temperature to trapped high-spin state

Kuppusamy,

Mizuno,

Spieker

et al. 2024

Preprint

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Spin-state switching in iron(II) complexes composed of ligands featuring moderate ligand-field strength—for example, 2,6-bi(1H-pyrazol-1-yl)pyridine (BPP)—is dependent on many factors—examples include lattice solvent, counter anion, and substituent. Herein, we show that spin-state switching in isomeric iron(II) complexes (1·CH3CN and 2) composed of tridentate all nitrogen coordinating ligands—ethyl 2,6-bis(1H-pyrazol-1-yl)isonicotinate (BPP-COOEt, L1) and (2,6-di(1H-pyrazol-1-yl)pyridin-4-yl)methylacetate (BPP-CH2OCOMe, L2)—is controlled by the nature of substituent at the fourth position of the pyridine ring of the BPP skeleton. Complex 1·CH3CN, crystallized with acetonitrile solvent, undergoes abrupt and hysteretic spin-state switching, hence bistable switching, with a thermal hysteresis width (ΔT1/2) of 44 K and switching temperature (T1/2) = 298 K in the first cycle. Conversely, the isomeric counterpart of 1·CH3CN—complex 2—crystallized with no lattice solvent; the complex was trapped in the high-spin (HS) state upon cooling from 300 K. Molecular structures of the LS and HS forms of complex 1·CH3CN revealed that spin-state switching induces a pronounced angular distortion, creating an energy barrier separating the LS and HS states. Traversing the barrier requires substantial molecular rearrangement in the presence of constraints imposed by the crystal lattice, rendering the spin-state switching of 1·CH3CN hysteretic in the solid-state. The observation of bistable spin-state switching with T1/2 centred at room temperature for 1·CH3CN as well as the attribution of pronounced angular distortion and conformational variation of the COOEt substituent as causes behind the observed hysteretic spin-state switching indicates that technologically relevant spin-state switching profiles based on mononuclear iron(II) complexes can be obtained.

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Field‐Induced Slow Magnetization Relaxation of a Tetrahedral S=2 Fe^IIS₄‐Containing Complex

Pissas,

Ferentinos,

Kyritsis

et al. 2024

ChemPlusChem

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In the work described herein, the spin relaxation properties of the mononuclear tetrahedral S = 2 [Fe{(SPiPr2)2N}2] complex (1) were studied by employing static and dynamic magnetic measurements al liquid helium temperatures. In the absence of an external direct current (DC) magnetic field, 1 exhibits fast magnetization relaxation. However, in the presence of external magnetic fields of a few kOe, slow relaxation is induced as monitored by alternating current (AC) magnetic susceptibility measurements up to 10 kHz, in the temperature range 2‐5 K. Analysis of the temperature dependence of the corresponding relaxation time reveals contributions by Quantum Tunnelling of Magnetization, and the Direct and Orbach processes in the magnetization relaxation mechanism of 1. The energy barrier, Ueff, of the Orbach process, as determined by this analysis, is compared with that related to the zero field splitting parameters of 1 which were previously determined by high‐ frequency and ‐field electron paramagnetic resonance and Mössbauer spectroscopies.

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Slow magnetic relaxation in Fe(ii)m-terphenyl complexes

Abstract: Two-coordinate transition metal complexes are exciting candidates for single molecule magnets (SMMs) because highly axial environments lead to sizeable magnetic anisotropy. We report a series of five structurally related two-coordinate...

Cited by 4 publications

References 73 publications

Lattice solvent- and substituent-dependent spin-crossover in isomeric iron(ii) complexes

Lattice solvent- and substituent-dependent spin-crossover in isomeric iron(ii) complexes

Substituent-dependent spin-state switching in isomeric iron(II) complexes: from bi-stable spin-state switching with T1/2 centred at room temperature to trapped high-spin state

Field‐Induced Slow Magnetization Relaxation of a Tetrahedral S=2 Fe^IIS₄‐Containing Complex

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Slow magnetic relaxation in Fe(ii)m-terphenyl complexes

Abstract: Two-coordinate transition metal complexes are exciting candidates for single molecule magnets (SMMs) because highly axial environments lead to sizeable magnetic anisotropy. We report a series of five structurally related two-coordinate...

Cited by 4 publications

References 73 publications

Lattice solvent- and substituent-dependent spin-crossover in isomeric iron(ii) complexes

Lattice solvent- and substituent-dependent spin-crossover in isomeric iron(ii) complexes

Substituent-dependent spin-state switching in isomeric iron(II) complexes: from bi-stable spin-state switching with T1/2 centred at room temperature to trapped high-spin state

Field‐Induced Slow Magnetization Relaxation of a Tetrahedral S=2 FeIIS4‐Containing Complex

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Field‐Induced Slow Magnetization Relaxation of a Tetrahedral S=2 Fe^IIS₄‐Containing Complex