Multiple spin phases in a switchable Fe(ii ) complex: polymorphism and symmetry breaking effects
| Autor: | Vadim Ksenofontov, Hao Hang, Ming-Liang Tong, Xin Bao, Il'ya A. Gural'skiy, Xiu Qin Chen, Bin Fei |
|---|---|
| Rok vydání: | 2018 |
| Předmět: |
Magnetic measurements
Materials science Spin transition 02 engineering and technology General Chemistry 010402 general chemistry 021001 nanoscience & nanotechnology Kinetic energy 01 natural sciences 0104 chemical sciences Crystallography chemistry.chemical_compound Polymorphism (materials science) chemistry Mössbauer spectroscopy Materials Chemistry Symmetry breaking 0210 nano-technology Single crystal Dicyanamide |
| Zdroj: | Journal of Materials Chemistry C. 6:3352-3361 |
| ISSN: | 2050-7534 2050-7526 |
| DOI: | 10.1039/c7tc05111e |
| Popis: | Polymorphism in spin-crossover (SCO) compounds allows accessing additional forms of switchable materials with diverse transition properties. We have prepared three polymorphs of a new complex [FeLBr(dca)2], where LBr is N,N′-bis[(5-bromo-2-pyridyl)methyl]ethane-1,2-diamine and dca is dicyanamide. They display different SCO properties: the α-form displays a hysteretic one-step switch centered at 134 K, the β-form undergoes hysteretic two-step spin transition with a plateau (T1/2 = 153 and 144 K) and the γ-form remains high spin (HS) over the whole temperature region. The kinetic origin of the hysteresis loop was demonstrated in temperature rate dependent magnetic measurements. Spin transition in the α-form is accompanied by symmetry breaking from a single Fe(II) site in the HS state to two distinct Fe(II) sites in the low spin (LS) state. In the β-form, the single crystal XRD has revealed a re-entrant symmetry change associated with the stepwise transition, with an ordered HS–LS alternating arrangement in the temperature plateau range. The corresponding Mossbauer study demonstrates a complicated evolution of spin transitions in the β-form through three different spin phases within different temperature regions. |
| Databáze: | OpenAIRE |
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