Unusual spin-transition anomaly in the crossover system [Fe(2-pic)3]Cl2·EtOH

Köppen, Herbert; Müller, Erwin W.; Köhler, C.P.; Spiering, H.; Meissner, Η.; Gütlich, Philipp

doi:10.1016/0009-2614(82)83298-3

Cited by 142 publications

(55 citation statements)

References 11 publications

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“…On the basis of previous publications on the thermal spin transition 2,3,21 as well as on the photophysical properties 8 of [Fe-(pic) 3 ]Cl 2 ‚EtOH, the results presented in this article lead to a quantitative, comprehensive, and consistent understanding of the various aspects of light-induced excited spin state trapping in this compound. In conclusion, all observations can be interpreted on the basis of comparatively simple and wellestablished theoretical concepts.…”

Section: Discussionmentioning

confidence: 69%

“…1 Because of cooperative effects of elastic origin, its thermal spin transition from the diamagnetic 1 A 1 (t 2g 6 ) lowspin state, which is thermodynamically stable at low temperatures, to the paramagnetic 5 T 2 (t 2g 4 e g 2 ) high-spin state, which becomes the thermodynamically stable state at elevated temperature, is comparatively abrupt. For [Fe(pic) 3 ]Cl 2 ‚EtOH, the actual spin transition temperature, that is, the temperature at which half the complexes are in the high-spin state, is ∼118 K. An intriguing feature of the thermal transition curve is the step of ∼7 K, 2 despite the fact that all complexes are crystallographically equivalent. Kohlhaas et al 3 explained this feature by taking into account short-range correlations with a nonrandom distribution of high-spin and low-spin complexes within the temperature interval of the step that results from specific nearest-neighbor interactions.…”

Section: Introductionmentioning

confidence: 99%

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Photoexcitation in the Spin-Crossover Compound [Fe(pic)₃]Cl₂·EtOH (pic = 2-Picolylamine)

2002

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[Fe(pic) 3 ]Cl 2 ‚EtOH (pic ) 2-picolylamine) is a spin-crossover compound that can be converted from the low-spin state to the high-spin state at temperatures below the thermal transition temperature by way of light irradiation in the visible part of the electromagnetic spectrum. For this compound, the question regarding the quantum efficiency of this photoconversion process and its possible dependence on irradiation intensity gave rise to some controversy. The experimental results presented in this paper demonstrate that the quantum efficiency of the photoconversion at 11 K is on the order of unity, with no noticeable dependence on irradiation intensity. It does, however, depend to some extent on the fraction of complexes already converted to the high-spin state.

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Section: Discussionmentioning

confidence: 69%

Section: Introductionmentioning

confidence: 99%

Photoexcitation in the Spin-Crossover Compound [Fe(pic)₃]Cl₂·EtOH (pic = 2-Picolylamine)

2002

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“…The first of these examples is the mononuclear complex [Fe(2-pic) 3 ]Cl 2 ·EtOH (2-pic = 2-picolyl-amine). [20] For this compound, there is only one crystallographically distinct iron center in both the HS state and in the LS state. [21] The nature of the intermediate phase formed in the plateau has been revealed in a recent detailed structural study performed over a wide range of temperatures.…”

Section: Resultsmentioning

confidence: 99%

Thermal‐ and Photoinduced Spin‐State Switching in an Unprecedented Three‐Dimensional Bimetallic Coordination Polymer

Niel

Thompson

Goeta

et al. 2005

Chemistry A European J

131

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The compound {Fe(pmd)[Ag(CN)2][Ag2(CN)3]} (pmd=pyrimidine) was synthesized and characterized. Magnetic, calorimetric and single crystal visible spectroscopic studies demonstrate the occurrence of a two-step high-spin (HS) low-spin (LS) transition. The critical temperatures are Tc1=185 and Tc2=148 K. Each step involves 50 % of the iron centers, with the low-temperature step showing a hysteresis of 2.5 K. The enthalpy and entropy variations associated with the two steps are H1=3.6±0.4 kJ mol-1 and S1=19.5±3 J K-1 mol-1; H2=4.8±0.4 kJ mol-1 and S2=33.5±3 J K-1 mol-1. Photomagnetic and visible spectroscopy experiments show that below 50 K, where the LS state is the thermodynamically stable state, the compound can be switched quantitatively to the HS state using green-red light (550-650 nm). HS-to-LS relaxation experiments in the dark at temperatures between 15 and 55 K show that the relaxation takes place via a two-step cooperative process, which was analyzed in the context of the mean field theory. The crystal structure has been studied at 290, 220, 170, 90 and 30 K together with 30 K after irradiation. The compound adopts monoclinic symmetry (P21/c, Z=16) at all temperatures. There are five [FeN6] pseudo-octahedral sites linked by pmd, [Ag(CN)2]- and [Ag2(CN)3]- bridging ligands to form an unprecedented three-dimensional (6,6) topology. The structural analysis allows for an understanding of the microscopic mechanism of the two-step behavior of the thermally induced spin transition as well as the corresponding relaxation of the photoexcited compound based on the individual changes of the five sites. Synergy between metallophilic interactions and the spin transition is also shown by the variation of the AgAg distances. Correlations between the variation of the unit-cell volume and the change of AgAg interactions within each step with the asymmetric change of the anomalous heat capacity have also been inferred

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“…Spiering and co-workers have systematically investigated the second coordination effect by a chemical substitution in ͓Fe͑2-pic͒ 3 ͔Cl 2 · EtOH [30][31][32] and ͓Fe͑ptz͒ 6 ͔͑BF 4 ͒ 2 . 33 They have found that the chemical substitution significantly modifies the LS-HS transudation temperature, and have ascribed the chemical impurity effect to the strain effect.…”

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confidence: 99%

Cooperative formation of high-spin species in a photoexcited spin-crossover complex

et al. 2006

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The dynamics of the photoinduced phase transition was investigated in a prototypical spin crossover complex, ͓Fe͑ptz͒ 6 ͔͑BF 4 ͒ 2 ͑ptz= 1-propyltetrazole͒, under photoexcitation at 77 K near the transition temperature ͑T c = 130 K͒. When the excitation power I exceeds Ϸ1 mW/mm 2 , we observed an "acceleration" of the creation rate of the density n HS of the high-spin ͑HS͒ species after a characteristic incubation period. The "acceleration" is interpreted in terms of the negative pressure effect; the photocreated HS species with a larger ionic radius expands the volume to cause the structural phase transition.

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Unusual spin-transition anomaly in the crossover system [Fe(2-pic)3]Cl2·EtOH

Cited by 142 publications

References 11 publications

Photoexcitation in the Spin-Crossover Compound [Fe(pic)₃]Cl₂·EtOH (pic = 2-Picolylamine)

Photoexcitation in the Spin-Crossover Compound [Fe(pic)₃]Cl₂·EtOH (pic = 2-Picolylamine)

Thermal‐ and Photoinduced Spin‐State Switching in an Unprecedented Three‐Dimensional Bimetallic Coordination Polymer

Cooperative formation of high-spin species in a photoexcited spin-crossover complex

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Unusual spin-transition anomaly in the crossover system [Fe(2-pic)3]Cl2·EtOH

Cited by 142 publications

References 11 publications

Photoexcitation in the Spin-Crossover Compound [Fe(pic)3]Cl2·EtOH (pic = 2-Picolylamine)

Photoexcitation in the Spin-Crossover Compound [Fe(pic)3]Cl2·EtOH (pic = 2-Picolylamine)

Thermal‐ and Photoinduced Spin‐State Switching in an Unprecedented Three‐Dimensional Bimetallic Coordination Polymer

Cooperative formation of high-spin species in a photoexcited spin-crossover complex

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Product

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Photoexcitation in the Spin-Crossover Compound [Fe(pic)₃]Cl₂·EtOH (pic = 2-Picolylamine)

Photoexcitation in the Spin-Crossover Compound [Fe(pic)₃]Cl₂·EtOH (pic = 2-Picolylamine)