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Issue 5, 2017
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Solvent modified spin crossover in an iron(III) complex: phase changes and an exceptionally wide hysteresis

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Abstract

Solvent effects in a series of Fe(III) spin crossover (SCO) complexes [Fe(qsal-I)2]OTf·sol (sol = MeOH 1, EtOH 2, n-PrOH 3, i-PrOH 4, acetone 5 and MeCN 6) are explored. SCO is abrupt in 1 (following MeOH loss) and 2, gradual for 3 (T1/2 = 199 K) and 4 (T1/2 = 251 K) and incomplete, even up to 350 K, for 5 and 6. In [Fe(qsal-I)2]OTf SCO occurs at T1/2↓ = 225 K and T1/2↑ = 234 K (ΔT = 9 K), while aged samples of 2 exhibit an exceptionally wide hysteresis of 80 K (T1/2↓ = 139 K and T1/2↑ = 219 K). In contrast, fresh samples of 2 exhibit stepped SCO with hysteresis varying from 2 to 42 K. VT-PXRD (variable temperature powder X-ray diffraction) studies indicate a new phase, 2b, is formed upon cooling below 180 K along with a minor LS phase 2c. Phase 2c and the HS phase 2a undergo a spin transition at T1/2↓ = 180 K and T1/2↑ = 215 K with phase 2b exhibiting two-step SCO. Structural studies in both spin states, except 6, show the cations are linked through extensive π–π interactions to form 1D chains. A combination of P4AE (parallel fourfold aryl embrace) and I⋯X (X = I, O, π) interactions create tightly packed 3D supramolecular networks. This study emphasizes that while solvent may result in only small structural changes SCO characteristics can be impacted dramatically.

Graphical abstract: Solvent modified spin crossover in an iron(iii) complex: phase changes and an exceptionally wide hysteresis

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Publication details

The article was received on 05 Dec 2016, accepted on 20 Mar 2017 and first published on 23 Mar 2017


Article type: Edge Article
DOI: 10.1039/C6SC05317C
Citation: Chem. Sci., 2017,8, 3949-3959
  • Open access: Creative Commons BY-NC license
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    Solvent modified spin crossover in an iron(III) complex: phase changes and an exceptionally wide hysteresis

    W. Phonsri, P. Harding, L. Liu, S. G. Telfer, K. S. Murray, B. Moubaraki, T. M. Ross, G. N. L. Jameson and D. J. Harding, Chem. Sci., 2017, 8, 3949
    DOI: 10.1039/C6SC05317C

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