A tetrathiafulvalene salt of the nitrite (NO) anion: investigations of the spin-Peierls phase

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2023-06, Vol.11 (24), p.817-8177
• Main Authors: Soriano, Loïc, Orio, Maylis, Pilone, Olivier, Jeannin, Olivier, Reinheimer, Eric, Quéméré, Nicolas, Auban-Senzier, Pascale, Fourmigué, Marc, Bertaina, Sylvain
• Format: Article
• Language: English
• Subjects: Anions; Chemical Sciences; Defects; Dimerization; Electron paramagnetic resonance; Inhomogeneity; Low temperature; Magnetic measurement; Material chemistry; Nitrogen dioxide; Superconducting quantum interference devices; Temperature dependence
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/d2tc05431k

Electrocrystallization of ortho -dimethyltetrathiafulvalene ( o -DMTTF) in the presence of a nitrite (NO 2 − ) anion affords a 2 : 1 phase, namely ( o -DMTTF) 2 NO 2 , the first example of an isolated cation radical salt with NO 2 − . The o -DMTTF molecule organizes into strongly dimerized stacks that adopt a rare chessboard organization, associated with a strongly 1D structure. As a consequence of dimerization, the salt exhibits a semiconducting behavior ( σ RT = 5 S cm −1 , E act = 0.1 eV). The bent NO 2 − anion is disordered on the inversion center but does not exhibit any anion-ordering transition. Combined SQUID magnetometry and electron paramagnetic resonance (EPR) experiments demonstrate the appearance of a spin-Peierls transition with T SP = 70 K. The temperature dependence of the spin gap and associated dimerization parameter δ across the spin-Peierls transition have been determined. The low-temperature narrow EPR line observed below T SP is attributable to intrinsic magnetic defects localized on the o -DMTTF molecules themselves. The broadening of the EPR line at higher magnetic fields is associated with the disordered NO 2 − anions surrounding these magnetic defects, contributing to the inhomogeneity of their g factor. The first nitrite salt of a tetrathiafulvalene derivative exhibits a rare chessboard-like organization of the conducting stacks, with a spin-Peierls transition at 70 K.