Gold and Nickel Extended Thiophenic-TTF Bisdithiolene Complexes.

Gold and nickel bisdithiolene complexes with methyl and tert -butyl substituted thiophenetetrathiafulavalenedithiolate ligands (α-mtdt and α-tbtdt) were prepared and characterized. These complexes were obtained, under anaerobic conditions, as tetrabutylammonium salts. The diamagnetic gold monoanion ( n -Bu₄N)[Au(α-mtdt)₂] ( 3 ) and nickel dianionic species ( n -Bu₄N) _x [Ni(α-mtdt)₂] (x = 1,2) ( 4 ) were similar to the related non-substituted extended thiophenic-TTF (TTF = tetrathiafulvalene) bisdithiolenes. However the introduction of the large, bulky substituent tert -butyl, led to the formation of a Au (I) dinuclear complex, ( n -Bu₄N)₂[Au₂(α-tbtdt)₂] ( 5 ). The neutral methyl substituted gold and nickel complexes were easily obtained through air or iodine exposure as polycrystalline or amorphous fine powder. [Au(α-mtdt)₂] ( 6 ) and [Ni(α-mtdt)₂] ( 7 ) polycrystalline samples display properties of a metallic system with a room temperature electrical conductivity of 0.32 S/cm and ≈4 S/cm and a thermoelectric power of ≈5 µV/K and ≈32 µV/K, respectively. While [Au(α-mtdt)₂] ( 6 ) presented a Pauli-like magnetic susceptibility typical of conducting systems, in [Ni(α-mtdt)₂] ( 7 ) large magnetic susceptibilities indicative of high spin states were observed. Both electric transport properties and magnetic properties for gold and nickel [M(α-mtdt)₂] are indicative that these compounds are single component molecular conductors.
Competing Interests: The authors declare no conflict of interest. The founding sponsors had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results.