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Issue 43, 2016
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Spin crossover and reversible single-crystal to single-crystal transformation behaviour in two cyanide-bridged mixed-valence {FeIII2FeII2} clusters

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Abstract

The reactions of tricyanometallate precursors, (Ph3PMe)[(Tp4-Me)Fe(CN)3·0.5CH3CN] (1) (Tp4-Me = tri(4-methyl-pyrazol-1-yl)borate) and (NBu4)[(MeTp)Fe(CN)3] (MeTp = methyltris(pyrazolyl)borate) with the presence of the tetradentate tpa ligand (tpa = tris(2-pyridylmethyl)amine) and Fe(ClO4)2·6H2O afford two new cyano-bridged mixed-valence {FeIII2FeII2} molecular squares: [(Tp4-Me)FeIII(CN)3]2[FeII(tpa)]2·2ClO4·H2O (2·H2O) and [(MeTp)FeIII(CN)3]2[FeII(tpa)]2·2ClO4·CH3OH (3·CH3OH). Solvent-exchange compounds of 3·CH3OH, [(MeTp)FeIII(CN)3]2[FeII(tpa)]2·2ClO4·2H2O (3·2H2O), and their solvent-free form (2 and 3) are also obtained, respectively. The spin crossover (SCO) properties of all compounds are confirmed by detailed structural analyses of the coordination environments of the FeII centres and magnetic susceptibility measurements. All compounds exhibit SCO behaviour near room temperature (T1/2 = 320 K for 2·H2O; 302 K for 2; 292 K for 3·CH3OH; 306 K for 3·2H2O and 290 K for 3) and reversible single-crystal to single-crystal (SC–SC) transformations induced by guest desorption and resorption or solvent exchange. The transition temperature close to room temperature can be tuned by the dehydration and re-hydration processes. The structure–property analysis discloses that the distorted {Fe4(μ-CN)4} core and deviations of bent ∠Fe−N[triple bond, length as m-dash]C angles play a key role in tuning the transition temperature of these similar mixed-valence {FeIII2FeII2} complexes.

Graphical abstract: Spin crossover and reversible single-crystal to single-crystal transformation behaviour in two cyanide-bridged mixed-valence {FeIII2FeII2} clusters

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Publication details

The article was received on 02 Sep 2016, accepted on 26 Sep 2016 and first published on 26 Sep 2016


Article type: Paper
DOI: 10.1039/C6DT03436E
Citation: Dalton Trans., 2016,45, 17254-17263
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    Spin crossover and reversible single-crystal to single-crystal transformation behaviour in two cyanide-bridged mixed-valence {FeIII2FeII2} clusters

    C. Zheng, J. Xu, F. Wang, J. Tao and D. Li, Dalton Trans., 2016, 45, 17254
    DOI: 10.1039/C6DT03436E

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