title: Synthesis, structure and electroluminescent properties of cyclometalated iridium complexes possessing sterically hindered ligands.
abstract: New CN donor ligands incorporating pyridine or benzoimidazole N donors and a sterically hindered cyclometalating aromatic core featuring a polyphenylenephenyl, fluoranthene, or triphenylene segment are prepared and successfully converted into heteroleptic iridium(III) cyclometalated complexes with acetylacetone auxiliary ligands. The X-ray structure of the complex, derived from a ligand containing a fluoranthene fragment, has been solved to unveil the corresponding structure. The results clearly demonstrate that the nature of the sigma-coordinating ligand segment plays a key role in dictating the emission profile and peak position, such that the emission hue has been successfully tuned ranging from green to red. Supplementary support of this viewpoint is also rendered by computational (DFT) approaches. Electroluminescent devices fabricated using a complex as dopant in the PVK matrix were found to exhibit bright greenish yellow emission with promising device characteristics (maximum brightness 26450 cd m(-2) at 30 V and a maximum current efficiency of 40 cd A(-1)).
authors.affiliation: Institute of Chemistry, Academia Sinica, 115 Nankang, Taipei, Taiwan.
authors.forename: Marappan
authors.initials: M
authors.lastname: Velusamy
authors.forename: K R Justin
authors.initials: KR
authors.lastname: Thomas
authors.forename: Chih-Hsin
authors.initials: CH
authors.lastname: Chen
authors.forename: Jiann T
authors.initials: JT
authors.lastname: Lin
authors.forename: Yuh S
authors.initials: YS
authors.lastname: Wen
authors.forename: Wan-Ting
authors.initials: WT
authors.lastname: Hsieh
authors.forename: Chin-Hung
authors.initials: CH
authors.lastname: Lai
authors.forename: Pi-Tai
authors.initials: PT
authors.lastname: Chou
mesh_terms: D018360:Crystallography, X-Ray; D004563:Electrochemistry; D007495:Iridium / Q000737:chemistry*; D008024:Ligands; D049408:Luminescent Agents / Q000138:chemical synthesis* / Q000737:chemistry; D047028:Macrocyclic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D013053:Spectrophotometry
chemical_list: D008024:Ligands; D049408:Luminescent Agents; D047028:Macrocyclic Compounds; D007495:Iridium