Stepwise Access of Emissive Ir(III) Complexes Bearing a Multi-Dentate Heteroaromatic Chelate: Fundamentals and Applications.

Three multi-dentate coordinated chelates L n H 2 ( n = 1, 2, and 3), comprising a linked 1-(pyridin-2-yl)ethylbenzene and one pyrazolyl pyridine unit and showing either tridentate or tetradentate coordination modes, are successfully designed and synthesized. Dinuclear Ir(III) complexes [Ir(κ 4 -L n )(μ-Cl)] 2 bearing tetradentate coordinated κ 4 -L n chelate ( 2a , n = 1; 2b , n = 2; 2c , n = 3) were next obtained en route from the respective intermediate [Ir(κ 3 -L n H)Cl(μ-Cl)] 2 bearing the tridentate coordinated κ 3 -L n H chelate ( 1a , n = 1; 1b , n = 2; 1c , n = 3). Next, mononuclear Ir(III) complexes Ir( κ 4 -L n )(thd) ( 3a , n = 1; 3b , n = 2; 3c , n = 3) with the tetradentate chelate were obtained upon treatment of 2 with 2,2,6,6-tetramethyl-3,5-heptanedione (thd)H in the presence of K 2 CO 3 . Concurrently, methylation of 2c in the presence of MeI and n Bu 4 NCl afforded tridentate Ir(κ 3 -L3HMe)Cl 3 ( 4 ) and, next, can be converted to tetradentate Ir( κ 4 -L3Me)Cl 2 ( 5 ) by further cyclometalation and HCl elimination in refluxing diethylene glycol monoethyl ether solution. The Ir(III) complexes 3a , 4 , and 5 were unambiguously identified using spectroscopic methods, together with single-crystal X-ray structural analyses on Ir(III) derivatives 3a , 4 , and 5 . Their photophysical and ,electrochemical properties and device fabrication properties were also investigated and compared with results from theoretical studies.