Photo- and Electroluminescent Neutral Iridium(III) Complexes Bearing Imidoylamidinate Ligands.

Imidoylamidinate-based heteroleptic bis(2-phenylbenzothiazole)iridium(III) and -rhodium(III) complexes [( bt ) 2 M(N ∩ N)] ( bt = 2-phenylbenzothiazole, N ∩ N = N '-(benzo[ d ]thiazol-2-yl)acetimidamidyl ( Ir1 and Rh1 ), N '-(6-fluorobenzo[ d ]thiazol-2-yl)acetimidamidyl ( Ir2 ), N '-(benzo[ d ]oxazol-2-yl)acetimidamidyl ( Ir3 ), N '-(1-methyl-1 H -benzo[ d ]imidazol-2-yl)acetimidamidyl ( Ir4 ); yields 70-84%) were obtained by the reaction of the in situ-generated solvento-complex [( bt ) 2 M(NCMe) 2 ]NO 3 and benzo[ d ]thia/oxa/ N -methylimidozol-2-amines in the presence of NaOMe. Complexes Ir1 - 4 exhibited intense orange photoluminescence, reaching 37% at room temperature quantum yields, being immobilized in a poly(methyl methacrylate) matrix. A photophysical study of these species in a CH 2 Cl 2 solution, neat powder, and frozen (77 K) MeOC 2 H 4 OH-EtOH glass matrix─along with density-functional theory (DFT), ab initio methods, and spin-orbit coupling time-dependent DFT calculations─verified the effects of substitution in the imidoylamidinate ligands on the excited-state properties. Electrochemical (cyclic voltammetry and differential pulse voltammetry) and theoretical DFT studies demonstrated noninnocent behavior of the imidoylamidinate ligands in Ir1 - 4 and Rh1 complexes due to the significant contribution coming from these ligands in the HOMO of the complexes. The iridium(III) species exhibit a ligand (L, 2-phenylbenzothiazole)-centered ( 3 LC), metal-to-ligand (L', imidoylamidinate) charge-transfer ( 3 ML'CT, 3 MLCT) character of their emission. The imidoylamidinate-based iridium(III) species were proved to be effective as the emissive dopant in an organic light-emitting diode device, fabricated in the framework of this study.