Interplay between Dopant Species and a Spin-Crossover Host Lattice during Light-Induced Excited-Spin-State Trapping Probed by Electron Paramagnetic Resonance Spectroscopy

Tumanov, S. G.; Veber, Sergey L.; Greatorex, Sam; Halcrow, Malcolm A.; Fedin, Matvey V.

doi:10.1021/acs.inorgchem.8b01096

Cited by 8 publications

(13 citation statements)

References 46 publications

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“…Doping iron(II) spin‐crossover materials with small quantities of isomorphous copper(II) dopants can provide a sensitive EPR spectroscopic probe of structural changes during spin‐crossover events . With that in mind, a mixed‐metal sample [Fe x Cu 1− x L 2 ][BF 4 ] 2 ⋅ 2 H 2 O ( 1Fe,Cu⋅ 2 H 2 O; x ≈0.97) was prepared by co‐crystallising the appropriate ratio of pre‐formed 1Fe and 1Cu from hot water, as before.…”

Section: Resultsmentioning

confidence: 91%

“…Doping iron(II) spin-crossover materials with small quantities of isomorphous copper(II) dopants can provide as ensitiveE PR spectroscopic probe of structuralc hanges durings pin-crossover events. [49][50][51] With that in mind, am ixed-metals ample [Fe x Cu 1Àx L 2 ][BF 4 ] 2 ·2H 2 O( 1Fe,Cu·2H 2 O; x % 0.97) was prepared by co-crystallising the appropriate ratio of pre-formed 1Fe and 1Cu from hot water,a sb efore.M agnetic measurements, TGA and DSC data confirmedt he compositiona nd spin state behaviourso f1Fe,Cu·2H 2 Oa nd anhydrous 1Fe,Cu are identical to the parent iron compounds ( Figures S2, S31 andS 33).…”

Section: Resultsmentioning

confidence: 99%

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Elucidating the Structural Chemistry of a Hysteretic Iron(II) Spin‐Crossover Compound From its Copper(II) and Zinc(II) Congeners

Pask

Greatorex

Kulmaczewski

et al. 2020

Chemistry A European J

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Annealing [FeL2][BF4]2⋅2 H2O (L=2,6‐bis‐[5‐methyl‐1H‐pyrazol‐3‐yl]pyridine) affords an anhydrous material, which undergoes a spin transition at T1/2=205 K with a 65 K thermal hysteresis loop. This occurs through a sequence of phase changes, which were monitored by powder diffraction in an earlier study. [CuL2][BF4]2⋅2 H2O and [ZnL2][BF4]2⋅2 H2O are not perfectly isostructural but, unlike the iron compound, they undergo single‐crystal‐to‐single‐crystal dehydration upon annealing. All the annealed compounds initially adopt the same tetragonal phase but undergo a phase change near room temperature upon re‐cooling. The low‐temperature phase of [CuL2][BF4]2 involves ordering of its Jahn–Teller distortion, to a monoclinic lattice with three unique cation sites. The zinc compound adopts a different, triclinic low‐temperature phase with significant twisting of its coordination sphere, which unexpectedly becomes more pronounced as the crystal is cooled. Synchrotron powder diffraction data confirm that the structural changes in the anhydrous zinc complex are reproduced in the high‐spin iron compound, before the onset of spin‐crossover. This will contribute to the wide hysteresis in the spin transition of the iron complex. EPR spectra of copper‐doped [Fe0.97Cu0.03L2][BF4]2 imply its low‐spin phase contains two distinct cation environments in a 2:1 ratio.

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Section: Resultsmentioning

confidence: 91%

Section: Resultsmentioning

confidence: 99%

Elucidating the Structural Chemistry of a Hysteretic Iron(II) Spin‐Crossover Compound From its Copper(II) and Zinc(II) Congeners

Pask

Greatorex

Kulmaczewski

et al. 2020

Chemistry A European J

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“…Since all of the SCO curves feature a sole step, the increase in T SCO must also involve the positive pressure induced on the [Fe(Mebpp) 2 ] 2+ complexes of the lattice by the other two species ([Fe-(Mebpp)(Me2bpp)] 2+ and [Fe(Me2bpp) 2 ] 2+ ) expected to undergo SCO at higher temperature. Once the positive pressure is overcome, the SCO occurs in a concerted manner (at a temperature lower than that expected for the species containing Me2bpp) as a result of an allosteric effect, 68 where the SCO of the [Fe(Mebpp) 2 ] 2+ centers induces the transition of the other two complexes present in the lattice. This is reminiscent of the synergy observed between SCO Fe(II) and Fe(III) anionic and cationic coordination species of a complex salt.…”

Section: Magnetic and Thermal Signatures Of Sco And Its C O O P E R A T I V I T Y T H E S O L I D S O L U T I O N S [ F E -(Mebpp) 2−2x mentioning

confidence: 99%

“…A very special case of this type of doping consists of incorporating structurally related complexes featuring both a different metal and different ligands but sufficiently close structurally to the host species to form solid solutions with it. In such cases, the influence of the SCO of the host on the properties of the guest is studied. ,− The doping approach, also termed molecular alloying, has been used only very rarely when the variable component is solely a ligand of the SCO complex rather than the metal or both. This variation affects the intermolecular interactions within the lattice while not diminishing the number of potential SCO centers.…”

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confidence: 99%

Allosteric Spin Crossover Induced by Ligand-Based Molecular Alloying

et al. 2020

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The spin crossover (SCO) phenomenon represents a source of multistability at the molecular level, and dilution into a nonactive host was originally key to understand its cooperative nature and the parameters governing it in the solid state. Here, we devise a molecular alloying approach in which all components are SCO-active, but with significantly different characteristic temperatures. Thus, the molecular material [Fe(Mebpp) 2 ](ClO 4 ) 2 (2) has been doped with increasing amounts of the ligand Me2bpp (Mebpp and Me2bpp = methyl-and bis-methyl-substituted bis-pyrazolylpyridine ligands), y i e l d i n g m o l e c u l a r a l l o y s w i t h t h e f o r m u l a [ F e -(Mebpp) 2−2x (Me2bpp) 2x ](ClO 4 ) 2 (4x; 0.05 < x < 0.5). The effect of the composition on the SCO process is studied through singlecrystal X-ray diffraction (SCXRD), magnetometry, and differential scanning calorimetry (DSC). While the attenuation of intermolecular interactions is shown to have a strong effect on the SCO cooperativity, the spin conversion was found to occur at intermediate temperatures and in one sole step for all components of the alloys, thus unveiling an unprecedented allosteric SCO process. This effect provides in turn a means of tuning the SCO temperature within a range of 42 K.

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“…While 1[ClO 4 ] 2 itself is not an SMM, 57 bistable multifunctional materials could still be produced from the 1[ClO 4 ] 2 host lattice containing functional dopant molecules. 64,65 Phase 2 of 1[BF 4 ] 2 shows a significant temperature dependence in its high-spin state (Figure 3). That reflects an increase of the monoclinic unit cell β angle at lower temperatures, which should reflect a gradual canting of the terpyridine embrace cation layers as the sample is cooled (Figure 2).…”

Section: ■ Conclusionmentioning

confidence: 99%

Spin-Crossover in a New Iron(II)/Di(pyrazolyl)pyridine Complex with a Terpyridine Embrace Lattice. Thermally Induced Excited Spin State Trapping and Clarification of a Structure–Function Correlation

Michaels

Berdiell

Vasili

et al. 2022

Crystal Growth & Design

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The complex salts [FeL 2]X2 (1X 2 ; L = 2,6-di{4-fluoropyrazol-1-yl}pyridine; X– = BF4 – or ClO4 –) exhibit abrupt spin-transitions with narrow thermal hysteresis, at T 1/2 = 164 K (X– = BF4 –) and 148 K (X– = ClO4 –). The transition in 1[ClO 4 ] 2 is complicated by efficient thermally induced excited spin-state trapping (TIESST) of its high-spin state below ca. 120 K, and the fully low-spin state was achieved only inside the magnetometer at a scan rate of 0.5 K min–1. Crystals of 1[BF 4 ] 2 are tetragonal (P 21 c, Z = 2; phase 1) at 300 K but transform to a highly twinned monoclinic phase 2 (P21, Z = 2) at 285 ± 5 K. These are forms of the “terpyridine embrace” crystal lattice, which often affords cooperative spin-transitions in iron/di(pyrazolyl)pyridine complexes. Phase 2 of high-spin 1[BF 4 ] 2 shows a significant temperature dependence by powder diffraction, which reflects increased canting of the monoclinic unit cell as the temperature is lowered. In contrast, 1[ClO 4 ] 2 retains phase 2 between 100 and 300 K, and was crystallographically characterized in its thermally trapped metastable high-spin state at 100 K, as well as its thermodynamic high- and low-spin forms at higher temperatures. The spin-crossover transition temperature in 1[ClO 4 ] 2 and related compounds correlates well with a parameter describing angular changes to the metal coordination sphere during the transition but not with other commonly used structural indices. The TIESST metastable high-spin state of 1[ClO 4 ] 2 shows no single molecule magnet properties at 2 K.

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Interplay between Dopant Species and a Spin-Crossover Host Lattice during Light-Induced Excited-Spin-State Trapping Probed by Electron Paramagnetic Resonance Spectroscopy

Cited by 8 publications

References 46 publications

Elucidating the Structural Chemistry of a Hysteretic Iron(II) Spin‐Crossover Compound From its Copper(II) and Zinc(II) Congeners

Elucidating the Structural Chemistry of a Hysteretic Iron(II) Spin‐Crossover Compound From its Copper(II) and Zinc(II) Congeners

Allosteric Spin Crossover Induced by Ligand-Based Molecular Alloying

Spin-Crossover in a New Iron(II)/Di(pyrazolyl)pyridine Complex with a Terpyridine Embrace Lattice. Thermally Induced Excited Spin State Trapping and Clarification of a Structure–Function Correlation

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