Alternative synthesis of (Z),(Z)-4,5;4′,5′-bis(1,4-dioxanediyl-2,3-dithio)tetrathiafulvalene (cis,cis-BDDT–TTF), and the preparation, EPR properties and structure of the radical cation salt (cis,cis-BDDT–TTF)2I3

Abstract

An alternative synthesis of the title compound (a derivative of BEDT–TTF or ET)via the cis-thione 1, which was unexpectedly obtained while attempting to prepare the trans isomer in the reaction between (E)-2,3-dichloro-1,4-dioxane and bis(4,5-dimercapto-1,3-dithiole-2-thione)zincate, is presented. The radical cation salt (cis,cis-BDDT–TTF)₂I₃ was prepared by electrochemical methods, and its structure, as determined by X-ray diffraction, consists of a columnar packing of the donor molecules with the triiodide anions residing between the columns. This structure is distinctly different from the layered structure, donor layers alternating with anion layers, of organic conductors and superconductors based on ET and related electron-donor molecules. The salt was found to exhibit a large EPR linewidth (130 G, g= 2.0045), which is much larger than those found in other organic conductors and superconductors. The large EPR linewidth may be a reflection of the three-dimensional (3D) electron delocalization, a consequence of the columnar structure of the salt.