Direct two-step spin-crossover through [HS–HS]⋯[LS–LS] at the plateau in dinuclear diiron(<scp>ii</scp>) complex [{Fe(NCBH3)(4phpy)}2(μ-bpypz)2]

Nakano, Katsutoshi; Kawata, Satoshi; Yoneda, K.; Fuyuhiro, Akira; Yagi, Takashi; Nasu, Saburo; Morimoto, Syotaro; Kaizaki, Sumio

doi:10.1039/b411190g

Cited by 118 publications

(101 citation statements)

References 19 publications

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“…7,8 Short-range correlations may also compete with long-range interactions and give rise to deviation from mean-field behaviors, 9 as evidenced in some cases by distinctive long relaxation tails from the LIESST state. 10 Although the vast majority of thermal spin transitions proceed in a single step, there has been an increasing number of two-step transitions reported for polymeric, [11][12][13][14][15][16][17] polynuclear, [18][19][20][21][22][23][24] or mononuclear SCO systems. [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] Such transitions result most frequently from the existence of two crystallographically (symmetrically) independent SCO Fe I I sites with slightly different coordination environments, leading to dissimilar transition temperatures delimiting a plateau (or shoulder), which usually occurs with an approximately equal populations of HS and LS species.…”

Section: Imentioning

confidence: 99%

Multimetastability, phototrapping, and thermal trapping of a metastable commensurate superstructure in a FeIIspin-crossover compound

et al. 2012

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The photoinduced switching and subsequent relaxation regime at cryogenic temperatures of the two-step spin-crossover compound [Fe(bapbpy)(NCS) 2 ] has been investigated by time-dependent photocrystallography. Upon photoexcitation from the low-spin (LS) state, a direct population of the metastable high-spin (HS) state occurs, without involving any intermediate structural state. The relaxation from the metastable HS state in isothermal conditions at 40 K proceeds in two successive steps associated with two symmetry breaking processes. The first step corresponds to the cooperative transformation to an intermediate superstructure, characterized by a long-range-ordered [HS-LS-LS] motif coupled to a commensurate displacive modulation, and concomitant with a tripling of the c axis of the unit cell (C2/c space group). The stabilization of the intermediate state is driven by strong molecule-lattice coupling. In the second stage, the intermediate state undergoes a transformation twinning triggered by lattice strain towards the LS state. The two-step relaxation is reminiscent of the two-step thermal transition of [Fe(bapbpy)(NCS) 2 ] and evidences multimetastability in the light-induced or relaxation regime. The long-range-ordered [HS-LS-LS] superstructure has also been trapped by rapid quench cooling to very low temperature, and has been structurally characterized.

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Section: Imentioning

confidence: 99%

Multimetastability, phototrapping, and thermal trapping of a metastable commensurate superstructure in a FeIIspin-crossover compound

et al. 2012

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“…In such a case, superstructure reflections should be observed since the structural rearrangement at the molecular level between HS and LS sites is important, as observed in ͓Fe͑2-picolylamine͒ 3 ͔Cl 2. EtOH, [26][27][28] or in some other compounds 29,30 as well. We looked carefully for such signatures in the diffraction data, but no change of translation symmetry was observed.…”

Section: Symmetry Of the Hs-ls Statementioning

confidence: 99%

Wavelength selective light-induced magnetic effects in the binuclear spin crossover compound{[Fe(bt)(NCS)2]2

et al. 2007

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Using Fourier transform infrared spectroscopy, x-ray diffraction, and magnetic susceptibility measurements under light irradiation, the selective light-induced excited spin state trapping ͑LIESST͒ and the reversible-LIESST effect have been evidenced and studied in depth in the binuclear spin crossover compound ͕͓Fe͑bt͒ ϫ͑NCS͒ 2 ͔ 2 bpym͖. In this system, each magnetic site can switch from low spin ͑LS͒ to high spin ͑HS͒, so that three states exist, namely, the LS-LS, HS-LS, and HS-HS. All these techniques shine a new light on the high phototunability of this system. In addition to the direct photoswitching from the LS-LS to the HS-LS or to the HS-HS state, here we show that photoinduced switching between the excited photoinduced states can be triggered in a reversible way: from HS-LS to HS-HS ͑irradiation around 800 nm͒, or reverse from HS-HS to HS-LS ͑irradiation around 1300 nm͒. The nature of the intermediate HS-LS state during the thermal and light-induced spin state changes is also discussed by comparing the spectroscopic measurements and the structural analysis. The loss of inversion symmetry in the HS-LS molecular state, where the two magnetic Fe sites are no more equivalent, is not accompanied by any long-range ordering of the noncentrosymmetric molecules in the crystal. Therefore the continuous double-step spin conversion corresponds to a double crossover.

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“…For example, the complex [Fe (2-pic) 3 ]Cl 2 ·EtOH (where 2-pic = 2-picolylamine) is a well-studied mononuclear SCO material in which the stepped spin transition shows a concomitant re-entrant phase transition with an ordered HS-LS intermediate phase (IP). 9 Subsequently several other examples of thermally induced stepped SCO accompanied by spontaneous crystallographic symmetry breaking have been reported, [10][11][12][13][14][15][16][17][18][19][20] revealing what was once thought to be a singular case of unusual SCO behavior might in fact be a rule. It is worth mentioning that a distinction should be made between magnetic symmetry breaking and crystallographic symmetry breaking accompanying the spin transition.…”

Section: Introductionmentioning

confidence: 99%

Pressure-induced two-step spin transition with structural symmetry breaking: X-ray diffraction, magnetic, and Raman studies

et al. 2011

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We have used single-crystal x-ray diffraction, Raman spectroscopy, and magnetometry to investigate the effect of hydrostatic pressures up to 16 kbar on the molecular spin crossover complex [Fe II (bapbpy)(NCS) 2 ]. A stepped first-order transition from the high-spin (HS) to low-spin (LS) phase was observed upon compression of single-crystal samples. The intermediate phase (IP) is stable between 4 and 11 kbar at room temperature. This phase is characterized by supercell reflections and tripling of the c-axis of the unit cell (C2/c) due to the formation of a periodic [HS-LS-LS] structural motif, as seen in the thermal stepped transition. The pressure-temperature phase diagram reveals an anomalous increase of the thermal hysteresis widths with increasing pressure and the stabilization of the IP across the investigated P-T space.

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Direct two-step spin-crossover through [HS–HS]⋯[LS–LS] at the plateau in dinuclear diiron(ii) complex [{Fe(NCBH₃)(4phpy)}₂(μ-bpypz)₂]

Cited by 118 publications

References 19 publications

Multimetastability, phototrapping, and thermal trapping of a metastable commensurate superstructure in a FeIIspin-crossover compound

Multimetastability, phototrapping, and thermal trapping of a metastable commensurate superstructure in a FeIIspin-crossover compound

Wavelength selective light-induced magnetic effects in the binuclear spin crossover compound{[Fe(bt)(NCS)2]2

Pressure-induced two-step spin transition with structural symmetry breaking: X-ray diffraction, magnetic, and Raman studies

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Direct two-step spin-crossover through [HS–HS]⋯[LS–LS] at the plateau in dinuclear diiron(ii) complex [{Fe(NCBH3)(4phpy)}2(μ-bpypz)2]

Cited by 118 publications

References 19 publications

Multimetastability, phototrapping, and thermal trapping of a metastable commensurate superstructure in a FeIIspin-crossover compound

Multimetastability, phototrapping, and thermal trapping of a metastable commensurate superstructure in a FeIIspin-crossover compound

Wavelength selective light-induced magnetic effects in the binuclear spin crossover compound{[Fe(bt)(NCS)2]2

Pressure-induced two-step spin transition with structural symmetry breaking: X-ray diffraction, magnetic, and Raman studies

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Direct two-step spin-crossover through [HS–HS]⋯[LS–LS] at the plateau in dinuclear diiron(ii) complex [{Fe(NCBH₃)(4phpy)}₂(μ-bpypz)₂]