Highly Stable Red-Light-Emitting Electrochemical Cells

The
synthesis and characterization of a series of new cyclometalated
iridium­(III) complexes [Ir­(ppy)2(N∧N)]­[PF6] in which Hppy = 2-phenylpyridine and N∧N is (pyridin-2-yl)­benzo­[d]­thiazole (L1), 2-(4-(tert-butyl)­pyridin-2-yl)­benzo­[d]­thiazole (L2), 2-(6-phenylpyridin-2-yl)­benzo­[d]­thiazole (L3), 2-(4-(tert-butyl)-6-phenylpyridin-2-yl)­benzo­[d]­thiazole (L4), 2,6-bis­(benzo­[d]­thiazol-2-yl)­pyridine
(L5), 2-(pyridin-2-yl)­benzo­[d]­oxazole
(L6), or 2,2′-dibenzo­[d]­thiazole
(L7) are reported. The single crystal structures of [Ir­(ppy)2(L1)]­[PF6]·1.5CH2Cl2, [Ir­(ppy)2(L6)]­[PF6]·CH2Cl2, and [Ir­(ppy)2(L7)]­[PF6] have been determined. The new complexes are efficient red
emitters and have been used in the active layers in light-emitting
electrochemical cells (LECs). The effects of modifications of the
2-(pyridin-2-yl)­benzo­[d]­thiazole ligand on the photoluminescence
and LEC performance have been examined. Extremely stable red-emitting
LECs are obtained, and when [Ir­(ppy)2(L1)]­[PF6], [Ir­(ppy)2(L2)]­[PF6],
or [Ir­(ppy)2(L3)]­[PF6] are used
in the active layer, device lifetimes greater than 1000, 6000, and
4000 h, respectively, are observed