Novel iridium complexes containing alkylfluorene functionalized picolinic acid ancillary ligand: Synthesis, optophysics and electroluminescence properties

• Two green-emitting cyclometalated iridium complexes were prepared.
• We investigated the optophysical properties of both iridium complexes.
• Both iridium complexes exhibited improving phase dispersibility in host matrix.
• Concentration quenching was effectively restrained by introducing bulk fluorene derivative.

Two novel green-emitting cyclometalated iridium complexes of (Buppy)2Ir(Tfl-pic) and (Buppy)2Ir(Brfl-pic) were synthesized and characterized, in which Buppy is 2-(4-tert-butylphenyl)pyridine, Tfl-pic is 6-(6′-(9″-octyl-2″,7″-bi(9,9-dioctylfluoren-2-yl)fluoren-9″-yl)hexyloxy) picolinic acid and Brfl is 6-(6′-(2″,7″-di-bromo-9″-octylfluoren-9″-yl)hexyloxy) picolinic acid. Their thermal property, dispersibility and optophysical properties were investigated. Both iridium complexes present intense UV absorption bands and photoluminescence performance in CH2Cl2. Single-emissive-layer polymer light-emitting devices using (Buppy)2Ir(Tfl-pic) and (Buppy)2Ir(Brfl-pic) as a single dopant and a blend of poly(vinylcarbazole) and 2-(4-biphenyl)-5-(4-tert-butyl-phenyl)-1,3,4-oxadiazole as the host matrix were fabricated. The (Buppy)2Ir(Tfl-pic)-doped devices exhibited a maximum current efficiency of 2.44 cd A−1. As expected, the phase separation and concentration quenching of these iridium complexes in the devices are efficiently suppressed due to appending bulky fluorene derivatives on the picolinic acid unit by a non-conjugated connection.

A novel green-emitting cyclometalated iridium complexes of (Buppy)2Ir(Tfl-pic) was synthesized and characterized. As expected, the phase separation and concentration quenching of this iridium complexes in the devices were efficiently suppressed due to the introduced bulky fluorene derivatives into the picolinic acid ancillary ligand by a non-conjugated connection.Figure optionsDownload as PowerPoint slide