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Książek M, Weselski M, Kaźmierczak M, Półrolniczak A, Katrusiak A, Paliwoda D, Kusz J, Bronisz R. Extremely Slow Thermally-Induced Spin Crossover in the Two-Dimensional Network [Fe(bbtr) 3 ](BF 4 ) 2. Chemistry 2024; 30:e202302887. [PMID: 37906679 DOI: 10.1002/chem.202302887] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Revised: 10/28/2023] [Accepted: 10/31/2023] [Indexed: 11/02/2023]
Abstract
Cooling [Fe(bbtr)3 ](BF4 )2 (bbtr=1,4-di(1,2,3-triazol-1-yl)butane) triggers very slow spin crossover below 80 K (T1/2 ↓ =76 K). The spin crossover (SCO) is accompanied by a hysteresis loop (T1/2 ↑ =89 K). In contrast to isostructural perchlorate analogue [Fe(bbtr)3 ](ClO4 )2 in which spin crossover during cooling is preceded by phase transition at TPT =126 K in tetrafluoroborate phase transition does not occur to the beginning of spin crossover (80 K). Studies of mixed crystals [Fe(bbtr)3 ](BF4 )2(1-x) (ClO4 )2x (0.5≤x≤0.9) showed that a phase transition precedes spin crossover, however, for x≅0.46 intersection of T1/2 (x) and TPT (x) dependencies takes place. The application of pressure of 1 GPa shifts the spin crossover in [Fe(bbtr)3 ](BF4 )2 to a temperature above 270 K. High-pressure studies of neat tetrafluoroborate and perchlorate, as well as mixed crystals [Fe(bbtr)3 ](BF4 )2(1-x) (ClO4 )2x (0.1≤x≤0.9), revealed that at 295 K P1/2 value changes linearly with x indicating similar mechanism of spin crossover under elevated pressure in all systems under investigation. Variable pressure single crystal X-ray diffraction studies confirmed that in contrast to thermally induced spin crossover undergoing differently in tetrafluoroborate and perchlorate an application of high pressure removes this differentiation leading to a similar mechanism depending at first on start spin crossover and then P-3→P-1 phase transition occurs. In this report we have shown that 2D coordination polymer [Fe(bbtr)3 ](BF4 )2 (bbtr=1,4-di(1,2,3-triazol-1-yl)butane) treated to date as spin crossover silent shows thermally induced spin crossover phenomenon. Spin crossover in tetrafluoroborate is extremely slow. Determination of the spin crossover curve required carrying measurement in the settle mode-cooling from 85 to 70 K took about 600 h (average velocity of change of temperature ca. 0.0004 K/min).
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Affiliation(s)
- Maria Książek
- Institute of Physics, University of Silesia, 75 Pułku Piechoty 1, 41-500, Chorzów, Poland
| | - Marek Weselski
- Faculty of Chemistry, University of Wrocław, F. Joliot-Curie 14, 50-383, Wrocław, Poland
| | - Marcin Kaźmierczak
- Faculty of Chemistry, University of Wrocław, F. Joliot-Curie 14, 50-383, Wrocław, Poland
| | - Aleksandra Półrolniczak
- Faculty of Chemistry, Adam Mickiewicz University in Poznań, Uniwersytetu Poznańskiego 8, 61-614, Poznań, Poland
| | - Andrzej Katrusiak
- Faculty of Chemistry, Adam Mickiewicz University in Poznań, Uniwersytetu Poznańskiego 8, 61-614, Poznań, Poland
| | - Damian Paliwoda
- European Spallation Source ERIC, Partikelgatan 2, 224 84, Lund, Sweden
| | - Joachim Kusz
- Institute of Physics, University of Silesia, 75 Pułku Piechoty 1, 41-500, Chorzów, Poland
| | - Robert Bronisz
- Faculty of Chemistry, University of Wrocław, F. Joliot-Curie 14, 50-383, Wrocław, Poland
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Burrage KC, Lin CM, Chen WC, Chen CC, Vohra YK. Experimental and Computational Studies on Superhard Material Rhenium Diboride under Ultrahigh Pressures. Materials (Basel) 2020; 13:E1657. [PMID: 32260069 DOI: 10.3390/ma13071657] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 03/27/2020] [Accepted: 03/31/2020] [Indexed: 11/29/2022]
Abstract
An emerging class of superhard materials for extreme environment applications are compounds formed by heavy transition metals with light elements. In this work, ultrahigh pressure experiments on transition metal rhenium diboride (ReB2) were carried out in a diamond anvil cell under isothermal and non-hydrostatic compression. Two independent high-pressure experiments were carried out on ReB2 for the first time up to a pressure of 241 GPa (volume compression V/V0 = 0.731 ± 0.004), with platinum as an internal pressure standard in X-ray diffraction studies. The hexagonal phase of ReB2 was stable under highest pressure, and the anisotropy between the a-axis and c-axis compression increases with pressure to 241 GPa. The measured equation of state (EOS) above the yield stress of ReB2 is well represented by the bulk modulus K0 = 364 GPa and its first pressure derivative K0´ = 3.53. Corresponding density-functional-theory (DFT) simulations of the EOS and elastic constants agreed well with the experimental data. DFT results indicated that ReB2 becomes more ductile with enhanced tendency towards metallic bonding under compression. The DFT results also showed strong crystal anisotropy up to the maximum pressure under study. The pressure-enhanced electron density distribution along the Re and B bond direction renders the material highly incompressible along the c-axis. Our study helps to establish the fundamental basis for anisotropic compression of ReB2 under ultrahigh pressures.
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