Luminescent and Redox-Active Iridium(III)-Cyclometalated Compounds with Terdentate Ligands.

Two novel bis-terdentate Ir(III)-cyclometalated complexes, Ir(L1)(L1(-)) (1) and Ir(L1(-))(2) (2), have been prepared (L1 is 2,6-bis(7'-methyl-4'-phenyl-2'-quinolyl)pyridine; L1(-) is its mono-anion, see Figure 1). To the best of our knowledge, 1 and 2 are the first luminescent and redox-active Ir(III)-cyclometalated bis-terdentate compounds. In acetonitrile solution, on oxidation, 2undergoes a reversible, metal-centered, one-electron oxidation at +1.40 V, whereas 1 does not exhibit any oxidation process up to +2.00 V. On reduction, both compounds undergo four reversible ligand-centered one-electron processes. The absorption spectra of the compounds are dominated by moderately intense (epsilon in the 10(3)-10(4) M(-)(1) cm(-)(1) range) spin-allowed metal-to-ligand charge-transfer (MLCT) bands at wavelengths longer than 350 nm and by intense (epsilon in the 10(4)-10(5) M(-)(1) cm(-)(1) range) ligand-centered (LC) bands at shorter wavelengths. The complexes exhibit an intense luminescence both at 77 K in MeOH/EtOH, 4:1 (v/v), rigid matrix (1, lambda(max) = 592 nm, tau = 20 &mgr;s; 2, lambda(max) = 598 nm, tau = 9 &mgr;s) and at room temperature in deoxygenated acetonitrile solution (1, lambda(max) = 620 nm, tau = 325 ns, Phi = 0.005; 2, lambda(max) = 630 nm, tau = 2.3 &mgr;s, Phi = 0.066). In all cases, the emission is assigned to triplet MLCT levels (namely, Ir --> L1 and Ir --> L1(-) in 1 and 2, respectively).