Molecular and Electronic Structure of Cyclic Trinuclear Gold(I) Carbeniate Complexes: Insights for Structure/Luminescence/Conductivity Relationships

An
experimental and computational study of correlations between
solid-state structure and optical/electronic properties of cyclotrimeric
gold­(I) carbeniates, [Au3(RNCOR′)3] (R, R′ = H, Me, nBu, or cPe), is reported.
Synthesis and structural and photophysical characterization of novel
complexes [Au3(MeNCOnBu)3], [Au3(nBuNCOMe)3], [Au3(nBuNCOnBu)3], and
[Au3(cPeNCOMe)3] are presented.
Changes in R and R′ lead to distinctive variations in solid-state
stacking, luminescence spectra, and conductive properties. Solid-state
emission and excitation spectra for each complex display a remarkable
dependence on the solid-state packing of the cyclotrimers. The electronic
structure of [Au3(RNCOR′)3] was
investigated via molecular and solid-state simulations. Calculations
on [Au3(HNCOH)3] models indicate that
the infinitely extended chain of eclipsed structures with equidistant
Au--Au intertrimer aurophilic bonding can have lower band gaps, smaller
Stokes shifts, and reduced reorganization energies (λ). The
action of one cyclotrimer as a molecular nanowire is demonstrated
via fabrication of an organic field effect transistor and shown to
produce a p-type field effect. Hole transport for the same cyclotrimerdoped
within a poly­(9-vinylcarbazole) hostproduced a colossal increase
in current density from ∼1 to ∼1000 mA/cm2. Computations and experiments thus delineate the complex relationships
between solid-state morphologies, electronic structures, and optoelectronic
properties of gold­(I) carbeniates.