The [(DT-TTF)2M(mnt)2] family of radical ion salts: From a spin ladder to delocalised conduction electrons that interact with localised magnetic moments

Elisabet Ribera, Concepció Rovira, Jaume Veciana, Judit Tarrés, Enric Canadell, Roger Rousseau, Elies Molins, Montserrat Mas, Jean Philippe Schoeffel, Jean Paul Pouget, Jorge Morgado, Rui T. Henriques, Manuel Almeida

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Abstract

Electrocrystallisation of the π-electron donor dithiopheno-tetrathiafulvalene (DT-TTF) with maleonitrile dithiolate (mnt)-metal (M) complexes gives rise to the new family of radical ion salts [(DT-TTF)2M(mnt)2] (M = Au, Pt, Ni), which are isostructural and crystallise in the monoclinic space group P21/n forming regular segregated stacks of donor and acceptor molecules along the b axis. The DT-TTF stacks are paired and interact strongly through S ⋯ S contacts in a ladder-like motif. The three salts have quite high room-temperature electrical conductivities (9, 40 and 40 S cm-1 for M = Au, Pt and Ni respectively) but their conductivity-temperature dependencies differ. The Au salt has an activated conductivity at room temperature whereas the Ni and Pt salts are metal-like at room temperature and both exhibit a metal-insulator transition around 120 K. These contrasting transport properties are accounted for by the differences in the transfer integrals along the DT-TTF stacks. The magnetic susceptibility of the salt with M = Au, in which the [Au(mnt)2-] anion is diamagnetic, can be fitted to a two-legged spin-ladder model. From diffuse X-ray scattering studies it is established that below 220 K the donors dimerise along the b stacking direction, and the spin carrier units in the ladder are identified as those formed by dimerised donors [(DT-TTF)2]. Observation in their EPR spectra of a single line which increases dramatically in width as the conductivity increases is evidence for the presence of two magnetic subsystems which interact in the salts (M = Ni, Pt) with paramagnetic [M(mnt)2]- ions.

Original languageEnglish
Pages (from-to)2025-2039
Number of pages15
JournalChemistry - A European Journal
Volume5
Issue number7
DOIs
Publication statusPublished - Jan 1 1999

Keywords

  • Conducting materials
  • Crystal engineering
  • Magnetic properties
  • Spin ladder
  • Tetrathiafulvalenes

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry

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    Ribera, E., Rovira, C., Veciana, J., Tarrés, J., Canadell, E., Rousseau, R., Molins, E., Mas, M., Schoeffel, J. P., Pouget, J. P., Morgado, J., Henriques, R. T., & Almeida, M. (1999). The [(DT-TTF)2M(mnt)2] family of radical ion salts: From a spin ladder to delocalised conduction electrons that interact with localised magnetic moments. Chemistry - A European Journal, 5(7), 2025-2039. https://doi.org/10.1002/(SICI)1521-3765(19990702)5:7<2025::AID-CHEM2025>3.0.CO;2-F