Effect of increasing pressure on the structure and temperature-induced changes in magnetic properties of heterospin comp
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Russian Chemical Bulletin, International Edition, Vol. 69, No. 8, pp. 1530—1536, August, 2020
Effect of increasing pressure on the structure and temperature-induced changes in magnetic properties of heterospin complexes* G. V. Romanenko,a G. A. Letyagin,a,b K. Yu. Maryunina,a,c A. S. Bogomyakov,a,b S. Nishihara,d K. Inoue,d and V. I. Ovcharenkoa,c aInternational
Tomography Center, Siberian Branch of the Russian Academy of Sciences, 3a ul. Institutskaya, 630090 Novosibirsk, Russian Federation. E-mail: [email protected] bNovosibirsk State University, 1 ul. Pirogova, 630090 Novosibirsk, Russian Federation cN. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky prosp., 119991 Moscow, Russian Federation. E-mail: [email protected] dDepartment of Chemistry, Graduate School of Science, and Chirality Research Center (CResCent), Hiroshima University, 1-3-1 Kagamiyama, Higashi Hiroshima, 739-8526, Japan The study is concerned with structural rearrangements in the crystals of heterospin complexes Cu(hfac)2 with nitroxide radicals LR (hfac is hexafluoroacetylacetonate, LR is 2-(1-R-1Hpyrazol-4-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl, R is Et or Allyl) induced by increasing pressure from 10–4 to ~1 GPa in the pressure-transmitting medium. An increase in the external pressure to only ~0.03 GPa leads to the disappearance of the temperature-induced magnetic anomaly observed for these heterospin crystals under ambient conditions. Key words: nitronyl nitroxide radicals, copper, hexafluoroacetylacetonate, crystal structure, magnetic properties, pressure.
Molecular magnets have attracted considerable interest due to sensitivity of these compounds to external stimuli and the prospects of their use as functional materials and in spintronic devices.1—5 Since these compounds are generally rich in organic component, they may be sensitive to an increase in the external pressure. Extremely high sensitivity to the applied external pressure was observed for the crystals of heterospin complexes of CuII hexafluoroacetylacetonate with nitronyl nitroxides, which can exhibit thermally induced phase transitions similar to spin-crossover. 6—8 Under ambient conditions, these transitions are accompanied by a structural rearrangement of two- {CuII—O•—NN—•O— CuII—O•—NN−•O−Cu(II)−O•−NN—•O−CuII—O•—N 2σ(I) Number of refined parameters GOOF Completeness of data (%) R1 wR2 (I > 2σ(I)) R1 wR2 (based on all reflections) CCDC
Value 0.23(5) С2/с 8 29.4239(11) 9.3895(3) 24.3583(18) 122.755(4) 5659.5(5) 1.711
0.32(5) С2/с 8 29.2577(12) 9.3230(3) 24.223(2) 122.863(4) 5549.9(6) 1.745
0.52(5) С2/с 8 29.1487(8) 9.2638(2) 24.1246(14) 122.970(3) 5465.2(4) 1.772
20845 2800 0.0555 28.312 1679 465 0.999 39.8 0.0540 0.1008 0.1168 0.1215 2006378
20582 2753 0.0529 28.667 1796 418 1.033 38.5 0.0649 0.1375 0.1133 0.1591 2006381
18647 2402 0.0542 28.214 1611 418 1.039 35.6 0.0694 0.1492 0.1141 0.1711 2006379
Table 4. Crystallographic data and the X-ray data collection and refinement statistics for [Cu(hfa
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