title: Unusual dinuclear and mononuclear cyclometalated iridium complexes of 2,5-diaryl-1,3,4-oxadiazole derivatives.
abstract: A family of new 2,5-diphenyl-1,3,4-oxadiazole (OXD) derivatives 8-11 bearing ortho-alkyl substituents on one of the phenyl rings is reported. The reactions of these OXDs with IrCl(3) under standard cyclometalating conditions did not give the usual μ-dichloro bridged diiridium OXD complexes. Instead, the novel diiridium complexes 12-14 and the monoiridium complex 15 were isolated and characterized by X-ray crystallography. It is proposed that the unusual structures arise because of the ortho-alkyl substituents leading to a substantial twisting of part of the OXD system which, for steric reasons, changes the normal course of the metal-ligand coordination reactions. Subsequent reactions of 13 and 15 gave the mononuclear complexes 16-18 with acac and picolinate anciliary ligands. The crystal structures of 16 and 18 are reported. Photoluminescence is observed in the green (16) and blue-green regions (17 and 18) at room temperature. Complexes 16-18 are phosphorescent at low temperature, with triplet lifetimes of 4.2-5.7 μs at 77 K.
authors.affiliation: Department of Chemistry, Durham University, South Road, Durham DH1 3LE, UK.
authors.forename: Yonghao
authors.initials: Y
authors.lastname: Zheng
authors.forename: Andrei S
authors.initials: AS
authors.lastname: Batsanov
authors.forename: Martin R
authors.initials: MR
authors.lastname: Bryce
mesh_terms: D018360:Crystallography, X-Ray; D003500:Cyclization; D007495:Iridium / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D010069:Oxadiazoles / Q000737:chemistry*
chemical_list: D009942:Organometallic Compounds; D010069:Oxadiazoles; D007495:Iridium