Molecular Alloys of Neutral Gold/Nickel Dithiolene Complexes in Single-Component Semiconductors

Control
of band filling or doping of molecular (semi)­conductors
can be performed by substitutional insertion of molecules with a similar
shape but a different electron count, with one more or one less electron.
This strategy has been explored here within the semiconducting, single-component,
radical gold dithiolene complex [AuOC4] bearing para-butoxyphenyl substituents.
Alloying with the corresponding neutral nickel dithiolene complex
[NiOC4] lacking one electron
afforded a complete isostructural series [NiOC4]1–x[AuOC4]x, spanning
the whole composition range from x = 0 to x = 1 by 0.1 increments, further characterized by X-ray
diffraction and EDX analyses. Magnetic susceptibility data confirm
the antiferromagnetic interactions between neighboring radical gold
dithiolene complexes. The electrical conductivity increases exponentially
with the x gold fraction, while the activation energy
remains constant in the more conducting, gold-rich samples. This behavior
is tentatively assigned to the tunneling barriers of variable width
(with x) but of constant height, separating more
conducting gold-rich segments. Comparison of redox potentials for
the 1e– oxidation and reduction of both [NiOC4] and [AuOC4] dithiolene complexes indicates that the [NiOC4] nickel complex does not act as a dopant
for the radical [AuOC4] complex.