Novel Iridium Complexes Containing Alkylfluorene Functionalized Picolinic Acid Ancillary Ligand: Synthesis, Optophysics and Electroluminescence Properties

Two novel green-emitting cyclometalated iridium complexes of (Buppy)(2)Ir(Tfl-pic) and (Buppy)(2)Ir(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)(2)Ir(Tfl-pic) and (Buppy)(2)Ir(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)(2)Ir(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. (C) 2014 Elsevier B.V. All rights reserved.