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

Chunyang Zheng; Juping Xu; Feng Wang; Jun Tao; Dongfeng Li

doi:10.1039/C6DT03436E

Spin crossover and reversible single-crystal to single-crystal transformation behaviour in two cyanide-bridged mixed-valence {Fe ^III₂Fe ^II₂} clusters†

Chunyang Zheng,‡^ab Juping Xu,‡^a Feng Wang,^c Jun Tao^d and Dongfeng Li*^ad

* Corresponding authors

^a College of Chemistry, Key Laboratory of Pesticide and Chemical Biology of Ministry of Education, Central China Normal University, 430079 Wuhan, P. R. China
E-mail: dfli@mail.ccnu.edu.cn

^b Hubei Collaborative Innovation Center for Rare Metal Chemistry, Hubei Key Laboratory of Pollutant Analysis and Reuse Technology, Institute for Advanced Materials, Hubei Normal University, 435002 Huangshi, P. R. China

^c College of Chemistry and Materials Science, Hubei Engineering University, 432000 Xiaogan, P. R. China

^d State Key Laboratory of Physical Chemistry of Solid Surfaces, Xiamen University, 361005 Xiamen, P. R. China

Abstract

The reactions of tricyanometallate precursors, (Ph₃PMe)[(Tp^4-Me)Fe(CN)₃·0.5CH₃CN] (1) (Tp^4-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 {Fe^III₂Fe^II₂} molecular squares: [(Tp^4-Me)Fe^III(CN)₃]₂[Fe^II(tpa)]₂·2ClO₄·H₂O (2·H₂O) and [(^MeTp)Fe^III(CN)₃]₂[Fe^II(tpa)]₂·2ClO₄·CH₃OH (3·CH₃OH). Solvent-exchange compounds of 3·CH₃OH, [(^MeTp)Fe^III(CN)₃]₂[Fe^II(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 Fe^II centres and magnetic susceptibility measurements. All compounds exhibit SCO behaviour near room temperature (T_1/2 = 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 {Fe^III₂Fe^II₂} complexes.

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Article information

DOI: https://doi.org/10.1039/C6DT03436E
Article type: Paper
Submitted: 02 Sep 2016
Accepted: 26 Sep 2016
First published: 26 Sep 2016

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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 {Fe^III₂Fe^II₂} 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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