Observation of a Hysteretic Phase Transition in a Crystalline Dinitroxide Biradical That Leads to Magnetic Bistability

Shultz, David A.; Fico, Rosario; Boyle, Paul D.; Kampf, Jeff W.

doi:10.1021/ja011341v

Cited by 35 publications

(31 citation statements)

References 26 publications

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“…As a result, these two crystals have become notable examples of magnetic bistability, a technologically relevant property that is sought--after 53,54 due to the memory effect intrinsically associated with a hysteresis loop. 55 Other organic radicals exhibiting magnetic bistability include additional 1,3,2-dithiazolyls 33,56 , bis--1,2,3--dithiazolyls 57,58 , nitroxides 59 , spirobiphenalenyls 60,61 , and dithiadiazolyls. 62,63 The hysteresis loop of 1 is centered around 323 K and spans 46 K (see Figure 1, right).…”

Section: Introductionmentioning

confidence: 99%

Two different mechanisms of stabilization of regular π-stacks of radicals in switchable dithiazolyl-based materials

et al. 2020

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Section: Introductionmentioning

confidence: 99%

Two different mechanisms of stabilization of regular π-stacks of radicals in switchable dithiazolyl-based materials

et al. 2020

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“…[1,2] The achievemento f ad eep understandingo ft he features governing the existence of bistability is an ecessary step towards the rational design of new bistable materials.Let us mention that bistability is merely as horterf orm for naming hysteretic spin-switch systems. [6][7][8][9][10][11][12][13][14][15][16][17] Among the purely organic radicals exhibitings pin-switch behavior, the family of dithiazolyl (DTA) neutralr adicals [18,19] is particularly interesting, as it has furnished numerouss witchable materials, some of them presenting hysteretic phaset ransitions, [6, 7, 10-12, 16, 20] and some of them presenting non-hysteretic phase transitions. However,i nh ysteretic spin-switch systems, the LT !HT transition takes place at ad ifferent temperature than that of the HT!LT transition.…”

Section: Introductionmentioning

confidence: 99%

“…At T < T c↓ , only the LT polymorph exists, whereas at T > T c↑ only the HT polymorph exists. Bistable materials based on transition‐metal complexes have been associated with spin transitions for many years, but recent work has demonstrated that purely‐organic radicals can also be versatile building blocks to achieve bistability …”

Section: Introductionmentioning

confidence: 99%

Bistability in Organic Magnetic Materials: A Comparative Study of the Key Differences between Hysteretic and Non‐hysteretic Spin Transitions in Dithiazolyl Radicals

Vela

Reardon

Jakobsche

et al. 2017

Chemistry A European J

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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⋅⋅⋅) and regular (⋅⋅⋅A⋅⋅⋅A⋅⋅⋅A⋅⋅⋅A⋅⋅⋅) π-stacks of radicals, respectively. We show that the regular π-stacks are not potential energy minima but average structures arising from a dynamic inter-conversion between two degenerate dimerized configurations: (⋅⋅⋅A-A⋅⋅⋅A-A⋅⋅⋅) ↔(-A⋅⋅⋅A-A⋅⋅⋅A-) . The emergence of this intra-stack 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⋅⋅⋅) ↔(-A⋅⋅⋅A-A⋅⋅⋅A-) 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.

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“…Most of the bistable compounds so far reported are based on transition metal ions [7][8][9] , but recent work 10 strongly suggests that organic radicals can also be at the forefront in the design and fabrication of the next generation of sensors and devices. Indeed, thiazyl- 11,12 , spiro-biphenalenyl- 13 and nitroxide-based radicals 14,15 have furnished striking examples of metal-free bistable materials whose phase transitions are accompanied by changes in the magnetic, optical and/or electrical response.…”

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confidence: 99%

The key role of vibrational entropy in the phase transitions of dithiazolyl-based bistable magnetic materials

et al. 2014

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The neutral radical 1,3,5-trithia-2,4,6-triazapentalenyl (TTTA) is a prototype of moleculebased bistable materials. TTTA crystals undergo a first-order phase transition between their low-temperature diamagnetic and high-temperature paramagnetic phases, with a large hysteresis loop that encompasses room temperature. Here, based on ab initio molecular dynamics simulations and new X-ray measurements, we uncover that the regular stacking motif of the high-temperature polymorph is the result of a fast intra-stack pair-exchange dynamics, whereby TTTA radicals continually exchange the adjacent TTTA neighbour (upper or lower) with which they form an eclipsed dimer. Such unique dynamics, observed in the paramagnetic phase within the whole hysteresis loop, is the origin of a significant vibrational entropic gain in the low-temperature to high-temperature transition and thereby it plays a key role in driving the phase transition. This finding provides a new key concept that needs to be explored for the rational design of novel molecule-based bistable magnetic materials.

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Observation of a Hysteretic Phase Transition in a Crystalline Dinitroxide Biradical That Leads to Magnetic Bistability

Cited by 35 publications

References 26 publications

Two different mechanisms of stabilization of regular π-stacks of radicals in switchable dithiazolyl-based materials

Two different mechanisms of stabilization of regular π-stacks of radicals in switchable dithiazolyl-based materials

Bistability in Organic Magnetic Materials: A Comparative Study of the Key Differences between Hysteretic and Non‐hysteretic Spin Transitions in Dithiazolyl Radicals

The key role of vibrational entropy in the phase transitions of dithiazolyl-based bistable magnetic materials

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