Polymorphism dependent light induced spin transition

Šalitroš, Ivan; Pogány, Lukáš; Rüben, Mario; Boča, Roman; Linert, Wolfgang

doi:10.1039/c4dt02421d

Cited by 25 publications

(20 citation statements)

References 23 publications

(6 reference statements)

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“…[30,44] While it occurs at a similar temperature to the compounds in this work, the spin-transition in 4 is more cooperative with a 8 K hysteresis loop, reflecting the involvement of the phase change in its SCO. While it is difficult to draw further comparison between 1-3 and 4, this emphasizes the structural complexity of the [Fe (bpp)2] 2+ system in this particular lattice type.…”

Section: Resultsmentioning

confidence: 91%

“…For all complexes, a drastic increase in the magnetic signal under green light irradiation was observed at 10 K. However, unusually for [Fe(bpp)2] 2+ derivatives, [7,20,[28][29][30] the photoconversion efficiency was not quantitative. The maximum MT values indicate photoconversion efficiencies of 70 % (for 1), 57 % (2) and 60 % (3).…”

Section: Resultsmentioning

confidence: 97%

“…[7,20,[28][29][30] The low spin high spin photoconversion was investigated on 1-3 in bulk condition using a SQUID magnetometer coupled to a CW optical source. The samples were irradiated at the following wavelengths: 405, 510, 640, 830 and 980 nm.…”

Section: Resultsmentioning

confidence: 99%

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Decoupled Spin Crossover and Structural Phase Transition in a Molecular Iron(II) Complex

Cook

Shepherd

Comyn

et al. 2015

Chemistry A European J

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Crystalline [Fe(bppSMe)2][BF4]2 (1; bppSMe=4‐(methylsulfanyl)‐2,6‐di(pyrazol‐1‐yl)pyridine) undergoes an abrupt spin‐crossover (SCO) event at 265±5 K. The crystals also undergo a separate phase transition near 205 K, involving a contraction of the unit‐cell a axis to one‐third of its original value (high‐temperature phase 1; Pbcn, Z=12; low‐temperature phase 2; Pbcn, Z=4). The SCO‐active phase 1 contains two unique molecular environments, one of which appears to undergo SCO more gradually than the other. In contrast, powder samples of 1 retain phase 1 between 140–300 K, although their SCO behaviour is essentially identical to the single crystals. The compounds [Fe(bppBr)2][BF4]2 (2; bppBr=4‐bromo‐2,6‐di(pyrazol‐1‐yl)pyridine) and [Fe(bppI)2][BF4]2 (3; bppI=4‐iodo‐2,6‐di(pyrazol‐1‐yl)‐pyridine) exhibit more gradual SCO near room temperature, and adopt phase 2 in both spin states. Comparison of 1–3 reveals that the more cooperative spin transition in 1, and its separate crystallographic phase transition, can both be attributed to an intermolecular steric interaction involving the methylsulfanyl substituents. All three compounds exhibit the light‐induced excited‐spin‐state trapping (LIESST) effect with T(LIESST=70–80 K), but show complicated LIESST relaxation kinetics involving both weakly cooperative (exponential) and strongly cooperative (sigmoidal) components.

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Section: Resultsmentioning

confidence: 91%

Section: Resultsmentioning

confidence: 97%

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Decoupled Spin Crossover and Structural Phase Transition in a Molecular Iron(II) Complex

Cook

Shepherd

Comyn

et al. 2015

Chemistry A European J

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“…Beyond SCO coordination polymers, discrete molecular SCO species incorporating imidazole- [16], pyrazole- [17] or pyridine-type [18,19,20] ligands have been shown to exhibit room temperature transitions with moderate thermal hysteresis widths [21]. Within the last decade, the iron(II) complexes with tridentate bis(pyrazole)pyridine [22,23,24,25,26,27,28,29,30,31,32,33] ligands have drawn increasing of attention to the field of SCO complexes. It has been shown that the modification of the ligand skeleton by substituents on the pyridine [23,24,25,26] or pyrazole [27] moiety leads to a fine-tuning of SCO properties.…”

Section: Introductionmentioning

confidence: 99%

“…Within the last decade, the iron(II) complexes with tridentate bis(pyrazole)pyridine [22,23,24,25,26,27,28,29,30,31,32,33] ligands have drawn increasing of attention to the field of SCO complexes. It has been shown that the modification of the ligand skeleton by substituents on the pyridine [23,24,25,26] or pyrazole [27] moiety leads to a fine-tuning of SCO properties. This is in fact a powerful tool for the synthesis of room temperature SCO compounds with anchoring functional substituents, which are tailor-made for the fabrication of hybrid materials, i.e., SCO surfaces [28] or SCO nanoparticles [29].…”

Section: Introductionmentioning

confidence: 99%

Solvent-Induced Polymorphism of Iron(II) Spin Crossover Complexes

2016

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Two new mononuclear iron(II) compounds (1) and (2) of the general formula [Fe(L)2](BF4)2·nCH3CN (L = 4-(2-bromoethyn-1-yl)-2,6-bis(pyrazol-1-yl)pyridine, n = 1 for (1) and n = 2 for compound (2)), were synthesized. The room temperature crystallization afforded concomitant formation of two different solvent analogues: compound (1) exhibiting triclinic P-1 and compound (2) monoclinic C2/c symmetry. Single-crystal X-ray studies confirmed the presence of the LS (low-spin) state for both compounds at 180 K and of the HS (high-spin) state for compound (2) at 293 K, in full agreement with the magnetic investigations for both solvent polymorphs. Compound (1) exhibits spin transition above 293 K followed by subsequent solvent liberation, while the spin transition of (2) takes already place at 237 K. After complete solvent removal from the crystal lattice, compound (1d) (the desolvated polymorph derived from (1)) exhibits spin transition centered at 342 K accompanied by a thermal hysteresis loop, while the analogous compound (2d) (the desolvated derivate of compound (2)) remains blocked in the HS state over all the investigated temperature range.

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Photoisomerization of Bis(tridentate) 2,6‐Bis(1H‐pyrazol‐1‐yl)pyridine Ligands Exhibiting a Multi‐anthracene Skeleton

Šalitroš

Fuhr

Gál³

et al. 2017

Chemistry A European J

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A novel molecular design is described where two peripheral moieties made of 2,6-bis(1H-pyrazol-1-yl)pyridine are linked through multi-1,8-diethynylanthracene moieties. The optimized synthesis of the three isostructural analogues 1 a, 1 b, and 1 c, containing the anthraquinone, anthracene, and 10-methoxyanthracene units, respectively, is reported. The resulting spatial face-to-face arrangement of the peripheral anthracene rings enables to trigger the intramolecular [4+4] photocycloaddition affording the isomers P1 b and P1 c, which can be thermally cleaved back to the original anthracene derivatives 1 b and 1 c, respectively. Single-crystal X-ray diffraction studies confirm the expected molecular structures of compounds 1 a-1 c as well as of their corresponding isomers P1 b and P1 c. The spectral, optical, and electrochemical properties of all synthesized compounds are investigated and discussed.

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Polymorphism dependent light induced spin transition

Cited by 25 publications

References 23 publications

Decoupled Spin Crossover and Structural Phase Transition in a Molecular Iron(II) Complex

Decoupled Spin Crossover and Structural Phase Transition in a Molecular Iron(II) Complex

Solvent-Induced Polymorphism of Iron(II) Spin Crossover Complexes

Photoisomerization of Bis(tridentate) 2,6‐Bis(1H‐pyrazol‐1‐yl)pyridine Ligands Exhibiting a Multi‐anthracene Skeleton

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