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Issue 17, 2012
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The interplay of iron(ii) spin transition and polymorphism

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The mononuclear compound (1) [FeII(L)2](BF4)2 (L = 4-ethynyl-2,6-bis(pyrazol-1-yl)pyridine) was prepared and structurally as well as magnetically characterised. The crystallisation revealed the formation of two polymorphs – the orthorhombic 1A and the tetragonal form 1B. A third, intermediate phase 1C was found exhibiting a different orthorhombic space group. Reversibility of the phase transition between 1A and 1C was studied by variable-temperature single-crystal and powder X-ray diffraction studies, while an irreversible phase transition was observed for the transition of 1B1C. The magnetic studies show that the 1A1C transition is accompanied by a very abrupt spin transition (ST) with 8 K hysteresis width (T1/2(↓) = 337 K, T1/2(↑) = 345 K). The ST was confirmed by Mössbauer spectroscopy as well as by DSC studies. In contrast, the 1B polymorph remained low-spin up to 420 K. In conclusion, a full cycle of intertwined phase- and spin-conversions of three polymorphs could be proven following the general scheme 1B1C1A.

Graphical abstract: The interplay of iron(ii) spin transition and polymorphism

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Article information

10 Oct 2011
08 Dec 2011
First published
30 Jan 2012

Dalton Trans., 2012,41, 5163-5171
Article type

The interplay of iron(II) spin transition and polymorphism

I. Šalitroš, O. Fuhr, A. Eichhöfer, R. Kruk, J. Pavlik, L. Dlháň, R. Boča and M. Ruben, Dalton Trans., 2012, 41, 5163
DOI: 10.1039/C2DT11906D

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