Blue-Emitting Dinuclear N-heterocyclic Dicarbene Gold(I) Complex Featuring a Nearly Unit Quantum Yield

Dinuclear N-heterocyclic dicarbene gold­(I) complexes
of general
formula [Au2(RIm-Y-ImR)2]­(PF6)2 (R = Me, Cy; Y = (CH2)1–4, o-xylylene, m-xylylene) have been synthesized
and screened for their luminescence properties. All the complexes
are weakly emissive in solution whereas in the solid state some of
them show significant luminescence intensities. In particular, crystals
or powders of the complex with R = Me, Y = (CH2)3 exhibit an intense blue emission (λmax = 450 nm)
with a high quantum yield (Φem = 0.96). The X-ray
crystal structure of this complex is characterized by a rather short
intramolecular Au···Au distance (3.272 Ǻ).
Time dependent density functional theory (TDDFT) calculations have
been used to calculate the UV/vis properties of the ground state as
well as of the first excited state of the complex, the latter featuring
a significantly shorter Au···Au distance.