Studies on a “Disappearing Polymorph”: Thermal and Magnetic Characterization of α-p-NCC6F4CNSSN•
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- 作者：Yassine Beldjoudi ; Ana Arauzo ; Fernando Palacio ; Melanie Pilkington ; Jeremy M. Rawson
- 刊名：Journal of the American Chemical Society
- 出版年：2016
- 出版时间：December 28, 2016
- 年：2016
- 卷：138
- 期：51
- 页码：16779-16786
- 全文大小：511K
- ISSN：1520-5126
文摘
The α-and β-phases of the thiazyl radical p-NCC6F4CNSSN• (1) can be selectively prepared by careful control of the sublimation conditions, with the α-phase crystallizing preferentially when the substrate temperature is maintained below −10 °C, whereas the β-phase is isolated when the substrate temperature is maintained at or above ambient temperature. Differential scanning calorimatry studies reveal that the α-phase converts to the β-phase upon warming over the range 111–117 °C (ΔH = +4 kJ·mol–1) via a melt–recrystallization process, with the β-phase itself melting at 167–170 °C (ΔHfus = 27 kJ·mol–1). IR and Raman spectroscopy can be used to clearly discriminate between 1α and 1β. The α-phase shows a broad maximum in the magnetic susceptibility around 8 K that, coupled with a broad maximum in the heat capacity, is indicative of short-range order. Some field dependence of the susceptibility below 3 K is observed, but the lack of features in the ac susceptibility, M vs H plots, or heat capacity mitigates against long-range order in 1α.