Decoupling anion-ordering and spin-Peierls transitions in a strongly one-dimensional organic conductor with a chessboard structure, (o-Me2TTF)(2)NO3 - Université de Rennes Accéder directement au contenu
Article Dans Une Revue International Union of Crystallography journal Année : 2018

Decoupling anion-ordering and spin-Peierls transitions in a strongly one-dimensional organic conductor with a chessboard structure, (o-Me2TTF)(2)NO3

Résumé

A mixed-valence conducting cation radical salt of the unsymmetrically substituted o-Me2TTF donor molecule (TTF is tetrathiafulvalene) was obtained upon electrocrystallization in the presence of the non-centrosymmetric NO3- anion. It crystallizes at room temperature in the monoclinic P2(1)/c space group, with the anion disordered on an inversion centre. The donor molecules are stacked along the a axis. A 90 degrees rotation of the longest molecular axis of o-Me2TTF generates a chessboard-like structure, preventing lateral S...S contacts between stacks and providing a strongly one-dimensional electronic system, as confirmed by overlap interaction energies and band structure calculations. A strong dimerization within the stacks explains the semiconducting behaviour of the salt, with sigma(room) (temp) = 3-5 S cm(-1) and E-activated = 0.12-0.14 eV. An X-ray diffuse scattering survey of reciprocal space, combined with full structure resolutions at low temperatures (250, 85 and 20 K), evidenced the succession of two structural transitions a ferroelastic one with an anion ordering (AO) process and the establishment of a (0, 1/2, 1/2) superstructure below 124 (+/- 3) K, also visible via resistivity thermal dependence, followed by a stack tetramerization with the establishment of a (1/2, 1/2, 1/2) superstructure below 90 (+/- 5) K. The latter ground state is driven by a spin-Peierls (SP) instability, as demonstrated by the temperature dependence of the magnetic susceptibility. Surprisingly, these two kinds of instability appear to be fully decoupled here, at variance with other tetramethyltetrathiafulvalene (TMTTF) or tetramethyltetraselenafulvalene (TMTSF) salts with such non-centrosymmetric counter-ions.
Fichier principal
Vignette du fichier
Jeannin-2018-Decoupling anion-ordering and spin-Peierls transitions.pdf (1.64 Mo) Télécharger le fichier
Origine : Fichiers éditeurs autorisés sur une archive ouverte
Loading...

Dates et versions

hal-01806936 , version 1 (17-07-2019)

Identifiants

Citer

Olivier Jeannin, Eric W. Reinheimer, Pascale Foury-Leylekian, Jean-Paul Pouget, Pascale Auban-Senzier, et al.. Decoupling anion-ordering and spin-Peierls transitions in a strongly one-dimensional organic conductor with a chessboard structure, (o-Me2TTF)(2)NO3. International Union of Crystallography journal, 2018, 5 (3), pp.361-372. ⟨10.1107/S2052252518004967⟩. ⟨hal-01806936⟩
125 Consultations
119 Téléchargements

Altmetric

Partager

Gmail Facebook X LinkedIn More