Electrical properties and electronic states of molecular conductors based on unsymmetrical organometallic-dithiolene gold(III) complexes.

The electronic properties of cation radical salts derived from organometallic mixed-ligand complexes [(ppy)Au(S−S)] (ppy− = C-dehydro-2-phenylpyridine(−); S−S2− = dithiolene ligand) with Au(III)−C σ-bond were investigated. A 2:1 salt complex [(ppy)Au(C8H4S8)]2[PF6] (C8H4S82− = 2-{(4,5-ethylenedithio)-1,3-dithiole-2-ylidene}−1,3-dithiole-4,5-dithiolate(2−)) exhibited semiconductive behavior under ambient pressure (ρrt = 2.6 Ω cm, Ea = 0.03 eV). Magnetic measurements show that it is a Mott insulator close to the metal−insulator boundary. Raman and infrared spectra have revealed that the complex has a quasi-one-dimensional dimeric structure consisting of uniformly charged donor molecules. The complex exhibits metallic behavior at pressures above 0.8 GPa. In contrast, a similar compound [(ppy)Au(C8H4S6O2)]2[BF4] (C8H4S6O22− = 2-{(4,5-ethylenedioxy)-1,3-dithiole-2-ylidene}-1,3-dithiole-4,5-dithiolate(2−)) is a band insulator.