Thermally Stimulated Delayed Phosphorescence (TSDP)-Based Gold(III) Complexes of Tridentate Pyrazine-Containing Pincer Ligand with Wide Emission Color Tunability and Their Application in Organic Light-Emitting Devices

A new class of pyrazine-based carbazole-containing
gold­(III) complexes
featuring thermally stimulated delayed phosphorescence (TSDP) properties
has been designed and synthesized. The emission colors are found to
be sensitive to the coordinating atom of the carbazolyl ligands at
the gold­(III) center, with emission energies spanning from green to
red. The efficiency of TSDP can be enhanced by lowering the polarity
of the solvent, as supported by the variable-temperature emission
and computational studies. Interestingly, a significant spectral shift
in electroluminescence with the change of Commission Internationale
de L’Eclairage (CIE) coordinates from (0.35, 0.60) to (0.44,
0.54) has been achieved by simply changing the host material from
CBP to TmPyPB. Solution-processable organic light-emitting devices
(OLEDs) have also been fabricated, with maximum current efficiencies
of up to 22.4 cd A–1 and maximum external quantum
efficiencies (EQEs) approaching 7.0%. A higher current efficiency
of 35.1 cd A–1 and EQE of 10.7% can be achieved
for the vacuum-deposited device based on 1, representing
the first demonstration of pyrazine-based tridentate ligand-containing
gold­(III) complexes as phosphorescent material for OLED application.