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

Three multi-dentate coordinated chelates LnH2(n=1,2, and 3), comprising a linked 1-(pyridin-2-yl)ethylbenzene and onepyrazolyl pyridine unit and showing either tridentate or tetradentate coordination modes, are successfully designed and synthesized.Dinuclear Ir(III) complexes [Ir(Kappa 4-Ln)(mu-Cl)]2bearing tetradentatecoordinated Kappa 4-Lnchelate (2a,n=1;2b,n=2;2c,n= 3) were nextobtained en route from the respective intermediate [Ir(Kappa 3-LnH)Cl(mu-Cl)]2bearing the tridentate coordinated Kappa 3-LnH chelate (1a,n=1;1b,n=2;1c,n= 3). Next, mononuclear Ir(III) complexes Ir(Kappa 4-Ln)(thd)(3a,n=1;3b,n=2;3c,n= 3) with the tetradentate chelate wereobtained upon treatment of2with 2,2,6,6-tetramethyl-3,5-heptane-dione (thd)H in the presence of K2CO3. Concurrently, methylation of2cin the presence of MeI andnBu4NCl afforded tridentate Ir(Kappa 3-L3HMe)Cl3(4) and, next, can be converted to tetradentate Ir(Kappa 4-L3Me)Cl2(5) by further cyclometalation and HCl elimination in refluxing diethylene glycol monoethyl ether solution. The Ir(III)complexes3a,4, and5were unambiguously identified using spectroscopic methods, together with single-crystal X-ray structura lanalyses on Ir(III) derivatives3a,4, and5. Their photophysical and ,electrochemical properties and device fabrication properties were also investigated and compared with results from theoretical studies.