Color tuning of cyclometalated 2-phenylbenzo[d]oxazole-based iridium(III) complexes through modification of different N^O ancillary ligands

•Four cyclometalated [Ir(bo)2(N^O)] complexes are synthesized.•Crystal structures of complexes 1, 2 and 4 are obtained.•The phosphorescent color tuning is dependent on the ancillary ligand structure.•The lowest-energy electronic transitions of absorption spectra are analyzed on the basis of DFT and TD-DFT.

Four new cyclometalated bo-based iridium(III) complexes with different N^O ancillary ligands, [Ir(bo)2pic] (1), [Ir(bo)2prz] (2), [Ir(bo)2bop] (3) and [Ir(bo)2btp] (4) (bo = 2-phenylbenzo[d]oxazole, pic = picolinate, prz = pyrazinate, bop = 2-benzoxazol-2-yl phenol, btp = 2-benzothiazol-2-yl phenol), have been synthesized and investigated by optical spectroscopy, electrochemistry as well as density functional theory (DFT). The crystal structures of 1, 2 and 4 have been determined, which show that each adopts the distorted octahedral coordination geometry. They exhibit intense green to orange phosphorescence (λmax = 531–598 nm) with quantum yields of 0.19–0.94 and lifetimes of 0.078–0.468 μs in solution at 298 K. The broad range color tuning of complexes 1–4 is dependent on the ancillary ligand structure. The cyclic voltammetry has been measured, showing a quasireversible, metal-centered oxidation with potentials at 1.00–1.49 V. The frontier molecular orbital diagrams and the lowest-energy electronic transitions of 1–4 have been calculated with density functional theory (DFT) and time-dependent DFT (TD-DFT).

Graphical abstractFour new cyclometalated iridium(III) complexes [Ir(bo)2(N^O)] (1–4) (N^O = pic, prz, bop and btp) have been synthesized and fully characterized. The photophysical and electrochemical properties of all complexes have been investigated, and the lowest-energy electronic transitions of absorption spectra have been analyzed by means of time-dependent density functional theory (TD-DFT).Figure optionsDownload full-size imageDownload as PowerPoint slide