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((NN)-N-boolean AND)] (bt = 2-phenylbenzothiazole, (NN)-N-boolean AND = 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-1H-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)]NO3 and benzo[d] thia/oxa/N-methylimidozol-2amines 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 CH2Cl2 solution, neat powder, and frozen (77 K) MeOC2H4OH-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 (3LC), metal-to-ligand (L', imidoylamidinate) charge-transfer ((ML)-M-3'CT,(MLCT)-M-3) 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.