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首页> 外文期刊>Chemistry: A European journal >Bistability in Organic Magnetic Materials: A Comparative Study of the Key Differences between Hysteretic and Non-hysteretic Spin Transitions in Dithiazolyl Radicals
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Bistability in Organic Magnetic Materials: A Comparative Study of the Key Differences between Hysteretic and Non-hysteretic Spin Transitions in Dithiazolyl Radicals

机译：有机磁性材料中的双稳态：二唑基滞后和非迟滞转型的关键差异的比较研究

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摘要

Dithiazolyl (DTA)-based radicals have furnished many examples of organic spin-transition materials, some of them occurring with hysteresis and some others without. Herein, we present a combined computational and experimental study aimed at deciphering the factors controlling the existence or absence of hysteresis by comparing the phase transitions of 4-cyanobenzo-1,3,2-dithiazolyl and 1,3,5- trithia-2,4,6-triazapentalenyl radicals, which are prototypical examples of non-bistable and bistable spin transitions, respectively. Both materials present low-temperature diamagnetic and high-temperature paramagnetic structures, characterized by dimerized (···A-A···A-A···)_n and regular (···A···A···A···A···)_n π-stacks of radicals, respectively. We show that the regular p-stacks are not potential energy minima but average structures arising from a dynamic inter-conversion between two degenerate dimerized configurations: (···A-A···A-A···)_n?(-A···A-A···A-)_n. The emergence of this intrastack dynamics upon heating gives rise to a second-order phase transition that is responsible for the change in the dominant magnetic interactions of the system. This suggests that the promotion of a (···A-A···A-A···)_n?(-A···A-A···A-)_n dynamics is a general mechanism for triggering spin transitions in DTA-based materials. Yet, this intra-stack dynamics does not suffice to generate bistability, which also requires a rearrangement of the intermolecular bonds between the π-stacks via a first-order phase transition.
机译：基于二唑基（DTA）的基团已经提供了许多有机旋转过渡材料的实例，其中一些存在于滞后和其他一些没有。在此，我们通过比较4-氰基苯-1,3,2-二唑基和1,3,5-三硫代唑基和1,3,5-三苯基 - 2的相转变，呈现旨在解读控制存在或不存在滞后的因素的组合计算和实验研究。 4,6-三己蕉基自由基，分别是非双稳态和双稳态旋转过渡的原型实例。这两种材料都存在低温抗磁性和高温顺磁结构，其特征在于二聚体（···AA···AA···）_N和常规（··············· ···分别是自由基的_·。我们表明，常规p堆栈不是潜在的能量最小值，而是由两个退化二聚体配置之间的动态转换产生的平均结构：（···AAIZIZIONALIZINGY）_N？（ - a···· aa···a - ）_ n。加热时，这种套管动力学的出现产生了二阶相转变，其负责系统的主导磁相互作用的变化。这表明促进A（···AA）......···）_N？（ - a···aa···a - ）_ n动力学是一种触发基于DTA的旋转过渡的一般机制。然而，这种堆栈内动态不足以产生双稳态，这也需要通过一阶相转变重新排列π叠层之间的分子间键。

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  • 来源
    《Chemistry: A European journal》 |2017年第14期|共11页
  • 作者

    Sergi Vela; Michael B. Reardon; Charles E. Jakobsche; Mark M. Turnbull; Jordi Ribas- Arino; Juan J. Novoa;

  • 作者单位

    Departament de Ciència de Materials i Química Física Universitat de Barcelona and IQTCUB Av. Diagonal 645 08028 Barcelona (Spain);

    Carlson School of Chemistry &

    Biochemistry Clark University 950 Main Street Worcester MA 01610 (USA);

    Carlson School of Chemistry &

    Biochemistry Clark University 950 Main Street Worcester MA 01610 (USA);

    Carlson School of Chemistry &

    Biochemistry Clark University 950 Main Street Worcester MA 01610 (USA);

    Departament de Ciència de Materials i Química Física Universitat de Barcelona and IQTCUB Av. Diagonal 645 08028 Barcelona (Spain);

    Departament de Ciència de Materials i Química Física Universitat de Barcelona and IQTCUB Av. Diagonal 645 08028 Barcelona (Spain);

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  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 应用化学;
  • 关键词

    computational chemistry; phase transitions; radicals; spin crossover;

    机译：计算化学;相变;自由基;旋转交叉;

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