Tuning the Energy Emission from Violet to Yellow with Bidentate Phosphine Gold(III) Complexes

The
synthesis and characterization of luminescent gold­(III) compounds,
obtained by coordination of the metal center to different phosphines,
is described. To avoid deactivation of luminescence by the presence
of low-energy d–d ligand field states in the gold­(III) center,
the ligands bonded to the metallic center have been carefully chosen,
among which we used bidentate phosphines with different numbers of
phenylene or alkynyl-phenylene spacers and pentafluorophenyl groups.
The reaction of [Au­(C6F5)3(tht)]
(tht = tetrahydrothiophene) with the corresponding diphosphines gave
the complexes [{Au­(C6F5)3}2­(1,4-PPh2(C6H4)nPPh2)] (n = 1–3)
and [{Au­(C6F5)3}2(PPh2CC­(C6H4)nCCPPh2)] (n = 0–2).
The study of their optical behavior reveals emission color variations
from violet to yellow for the compounds containing the phosphines
with one, two, and three phenylene spacers, respectively, and much
more fine-tuning, from deep blue to brilliant blue for those intercalating
alkynyl and phenylene spacers. Four of the new complexes were also
characterized by X-ray diffraction crystallography, showing supramolecular
structures formed through hydrogen bonding.