Phosphorescent Iridium(III) Cyclometalates Supported by 2-(1,2-Dihydronaphthalen-4-yl)pyridine Ligand

摘要

Novel Ir(III) cyclometalates, (dnpy)(2)Ir(acac) (2) and fac-Ir(dnpy)(3) (3), supported by 2-(1,2-dihydronaphthalen- 4-yl) pyridyl ligand (dnpy) were synthesized and characterized. X-ray diffraction study on 3 revealed facial arrangement of three dnpy ligands around the Ir center. Photoluminescence (PL) spectra of 2 exhibited orange emission centered at 590 nm, which is almost similar to that observed for 2naphthylpyridine complex, (napy) 2Ir(acac) (III). In contrast, compound 3 displayed blue-shifted, yellow emission at 550 nm. Tris-complex 3 showed higher quantum efficiencies than 2 in both the solution and film states. Cyclic voltammetry measurements indicated that replacing naphthyl with 1,2-dihydronaphthyl ring raises both the metal-centered HOMO level and ligand-centered LUMO level in 2 and 3. It was suggested that 1,2-dihydronaphthyl ring has a stronger electron-donating effect than naphthyl ring, while the p* orbital of dnpy ligand is less stabilized due to partial conjugation of the dihydronaphthyl ring.