Two electrically different molecular conductors based on unsymmetrical Au(III)-Dithiolene complexes with similar crystal structures

The cation radical salt based on unsymmetrical metal-dithiolene complexes [Au(ppy)(C ₈H ₄S ₈)] ₂[PF ₆] (1) is a semiconductor with small activation energy under ambient pressure, and shows metallic behavior under high pressure. On the other hand, [Au(ppy)(C ₈H ₄ S ₆O ₂)] ₂[BF ₄] (2) is an insulator in spite of the structural similarity. Effective conduction pathways through the S⋯S contacts were found in the crystal structure of 1. However, the crystal of 2 contains no such conduction pathways. Comparison of the energy band structures of 1 and 2 suggests that even a subtle difference in cation arrangements makes a remarkable difference between the electrical properties of 1 and 2.