Radical cation salts of TTF derivatives incorporating the maleonitriledithiolate copper cluster anion [Cu8(i-mnt)6]4−

Abstract

The synthesis by electrocrystallization and X-ray crystal structures of two radical cation salts, (BEDT-TTF)₆[Cu₈(i-mnt)₆]·(CH₂Cl₂)₄2 and (EDT-TTF)₆[Cu₈(i-mnt)₆] 3 are described. These salts incorporate the isomaleonitriledithiolato–octa-copper(I) complex [Cu₈(i-mnt)₆]⁴⁻ as anion and the bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF), or the ethylenedithiotetrathiafulvalene (EDT-TTF) as radical cations. The crystal structure of the starting material (n-Pr₄N)₄[Cu^I₈(i-mnt)₆]·(MeCN)₂1 is also reported. In 2, organic molecules form isolated fully oxidized (BEDT-TTF)₂²⁺ dimers and mixed valence (BEDT-TTF)₂^1+˙ dimers, the latter assembled in chains along the a-axis. The crystal structure of 3 is composed of layers of anions and cations, the latter incorporate fully oxidized (EDT-TTF)₂²⁺ dimers and neutral EDT-TTF molecules. For both salts, interactions between organic molecules were rationalized by extended Hückel calculations. 2 exhibits a low conductivity at room temperature. This study shows that metal dithiolate clusters are a new class of anions suitable for the preparation of TTF-based molecular materials.