Room-Temperature Magnetic Bistability in a Salt of Organic Radical Ions

Abstract

Cocrystallization of 7,7′,8,8′-tetracyanoquinodimethane radical anion (TCNQ–•) and 3-methylpyridinium-1,2,3,5-dithiadiazolyl radical cation (3-MepyDTDA+•) afforded isostructural acetonitrile (MeCN) or propionitrile (EtCN) solvates containing cofacial π dimers of homologous components. Loss of lattice solvent from the diamagnetic solvates above 366 K affords a high-temperature paramagnetic phase containing discrete TCNQ–• and weakly bound π dimers of 3-MepyDTDA+•, as evidenced by X-ray diffraction methods and magnetic susceptibility measurements. Below 268 K, a first-order phase transition occurs, leading to a low-temperature diamagnetic phase with TCNQ–• σ dimer and π dimers of 3-MepyDTDA+•. This study reveals the first example of cooperative interactions between two different organic radical ions leading to magnetic bistability, and these results are central to the future design of multicomponent functional molecular materials.

Magnetic bistable organic ionic plastic crystal with room temperature ion conductivity comparable to NASICON and superionic conduction in a broad temperature window

“…To this end, in previous study, we proposed a strategy for the design of a new type of OIPCs, 25 i.e., to achieve OIPCs by combining metal bis-1,2-dithiolene ([M(dithiolato) 2 ] À anion; M = Ni, Pd, or Pt ion) with conventional globular-shaped cations, because the negative charge is distributed on the whole molecule skeleton in a planar p-electron delocalized [M(dithiolato) 2 ] À anion, minimizing interionic Coulomb interactions, which reduces both the lattice energy and rotational barrier of spherical cations. Moreover, this strategy may offer the OIPCs magnetic bistability, 19,24,26,27 owing to S = 1 2 [M(dithiolato) 2 ] À anions preferring to form columnar stacks wherein the strong spin-lattice interplays promote spin-Peierls-type transition; besides this, the columnar anion stacks also provide robust frameworks owing to strong antiferromagnetic (AFM) couplings in a stack, which are beneficial for ion migration and improve the disadvantage of multiple plastic crystal phases in the conventional 'discrete' ion plastic crystals as well. 25 Herein, we report the third member in this new type of OIPC family, [DEIm][Ni(mnt) 2 ] (1), with two-step solid-solid phase transitions prior to melting, i.e., crystal-crystal transformation in the lower temperature region coupled with magnetic bistability and negative thermal expansion; crystal-plastic crystal phase transition in the higher temperature regime.…”

Reversible Switchability of Magnetic Anisotropy and Magnetodielectric Effect Induced by Intermolecular Motion

“…[9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] More importantly, accompanied by the switch of magnetic properties, the explicit structural changes of the molecule draw extensive attention thanks to its beneficial insights into the magneto-structural correlations hidden in phase transition and further shed light on the design tactics. [25][26][27][28][29][30][31][32][33][34] Similarly, the field of artificial molecular machines (AMMs) with switchable properties has also developed rapidly in the past few decades. [35,36] One of the key purposes is to achieve the control of motions at the molecular level through external stimuli to affect macroscopic physical properties.…”

Reversible Switchability of Magnetic Anisotropy and Magnetodielectric Effect Induced by Intermolecular Motion

“…[9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] More importantly, accompanied by the switch of magnetic properties, the explicit structural changes of the molecule draw extensive attention thanks to its beneficial insights into the magneto-structural correlations hidden in phase transition and further shed light on the design tactics. [25][26][27][28][29][30][31][32][33][34] Similarly, the field of artificial molecular machines (AMMs) with switchable properties has also developed rapidly in the past few decades. [35,36] One of the key purposes is to achieve the control of motions at the molecular level through external stimuli to affect macroscopic physical properties.…”

“…The magnetic properties of switchable molecular materials, such as spin transition, valence tautomerism, etc., strongly couple to external perturbations and display a variety of controllable stimulus‐response behaviors triggered by heat, light, or pressure [9–24] . More importantly, accompanied by the switch of magnetic properties, the explicit structural changes of the molecule draw extensive attention thanks to its beneficial insights into the magneto‐structural correlations hidden in phase transition and further shed light on the design tactics [25–34] …”