Issue 5, 2017

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

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

Supplementary files

Article information

Article type
Edge Article
Submitted
05 Dec 2016
Accepted
20 Mar 2017
First published
23 Mar 2017
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2017,8, 3949-3959

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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