Synthesis, structures, and properties of iridium(III) bis-cyclometallated complexes containing three-atom chelates

Heating of [Ir(η2-ppy)2(MeCN)2]NO3 (1, ppy = 2-phenylpyridine) in MeCN under reflux afforded [Ir(η2-ppy)2(η2-NO3)] (2). Treatment of 1 with 2-mercaptopyridine (Hmp), 6-methyl-2-hydroxypyridine (Hmhp), 6-chloro-2-hydroxypyridine (Hchp), trimethylacetic acid (Htma), benzoic acid (Hbz), 2-methylacrylic acid (Hma), and acetic acid (Hac) in the presence of excess Et3N produced [Ir(η2-ppy)2(η2-XZY)] (XZY− = mp− (3), mhp− (4), chp− (5), ac− (6), bz− (7), ma− (8), tma− (9)). Crystal structures of 2, 3, 7, 8, and 9 have been characterized by X-ray diffraction. The inherent strain contained in the four-member rings, {Ir(η2-XZY)}, is apparently reflected in the long Ir–X and Ir–Y distances. The absorption and emission properties of nearly all the new complexes except 2 show small variations.