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Issue 39, 2011
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A temperature-dependent order-disorder and crystallographic phase transition in a 0D Feii spin crossover compound and its non-spin crossover Coiiisomorph

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Abstract

The new dipyridylamino/triazine ligand DDE (N2,N2,N4,N4-tetraethyl-N6,N6-di(pyridin-2-yl)-1,3,5-triazine-2,4,6-triamine) has been incorporated into the mononuclear FeIISCO compounds cis-[FeII(NCSe)2(DDE)2] (1), cis-[FeII(NCBH3)2(DDE)2] (2), and cis-[FeII(NCS)2(DDE)2] (3). Magnetic susceptibility measurements reveal that each of 1, 2 and 3 undergoes a complete, continuous spin transition with a T½ of ∼260 K, ∼300 K and ∼205 K, respectively. An analogue and isomorph of 1, cis-[CoII(NCSe)2(DDE)2] (4), remains high spin down to low temperatures. Variable temperature single crystal data reveal that 1 and 4 undergo a crystallographic phase transition (from orthorhombic Pbcn at high temperatures to monoclinic P2/c at low temperatures) accompanied by an order-disorder transition of ethyl moieties of the DDE ligand. In the Pbcn phase, the structures of 1 and 4 contain one crystallographically unique MII centre, while in the P2/c phase, 1 and 4 contain two crystallographically unique MII centres. Variable temperature powder X-ray diffraction experiments reveal that the crystallographic phase transition occurs at ∼250 K for 1. The occurrence of the concomitant order-disorder and crystallographic phase transitions undergone by 1 and 4 is not directly apparent in their magnetic susceptibility measurements, and this is likely due to the local environment of the MII centres remaining largely undisturbed as the transitions occur. The compound 2 is isostructural to 1 and 4 at low temperatures.

Graphical abstract: A temperature-dependent order-disorder and crystallographic phase transition in a 0D Feii spin crossover compound and its non-spin crossover Coiiisomorph

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Supplementary files

Article information


Submitted
23 May 2011
Accepted
19 Jul 2011
First published
06 Sep 2011

Dalton Trans., 2011,40, 10147-10155
Article type
Paper

A temperature-dependent order-disorder and crystallographic phase transition in a 0D FeII spin crossover compound and its non-spin crossover CoIIisomorph

T. M. Ross, B. Moubaraki, K. S. Wallwork, S. R. Batten and K. S. Murray, Dalton Trans., 2011, 40, 10147
DOI: 10.1039/C1DT10961H

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