Jump to main content
Jump to site search

Issue 4, 2013
Previous Article Next Article

Guanidinate ligated iridium(iii) complexes with various cyclometalated ligands: synthesis, structure, and highly efficient electrophosphorescent properties with a wide range of emission colours

Author affiliations

Abstract

We report the synthesis, structure, and electrophosphorescence properties of a series of heteroleptic iridium(III) complexes with various cyclometalated (C⁁N) ligands based on the sterically demanding guanidinate ancillary ligand. The iridium(III) complexes contain two cyclometalated (C⁁N) ligands and one monoanionic guanidinate ancillary ligand [(NiPr)2C(NPh2)]. The reaction of the bis(C⁁N) iridium(III) chloride [(C⁁N)2Ir(μ-Cl)]2 with the lithium salt of guanidine ligand [Li{(NiPr)2C(NPh2)}] at 80 °C gave a 65–85% yield of the corresponding heteroleptic [(C⁁N)2Ir{(NiPr)2C(NPh2)}] complexes with several different cyclometalated (C⁁N) ligands such as 2-phenylpyridine (ppy) (1), 2-(2,4-diflurophenyl)pyridine (dfppy) (2), 2-(p-tolyl) pyridine (tpy) (3), benzoquinoline (bzq) (4), 2-phenylbenzoxazole (box) (5), 2-phenylbenzothiazole (btz) (6), 2-(2′-benzothienyl)pyridine (btp) (7) and 1-phenylisoquinoline (piq) (8). These heteroleptic cyclometalated (C⁁N) iridium(III) complexes showed intense absorption bands in the UV region, assignable to ligand-centered (π–π*) transitions and lower energy absorption bands that extended to the visible region are mainly derived from spin-forbidden ligand-centered (π–π*) transitions, as well as metal-to-ligand charge transfer (MLCT) transitions. These complexes also showed intense emissions at room temperature, leading to λmax values from green (λ = 505 nm) to a perfect red colour (λ = 655 nm) with quantum yields (Φ) of 0.18 to 0.64 and phosphorescence lifetimes of 0.78 to 5.80 μs. Organic light-emitting diodes (OLEDs) were fabricated by the use of these complexes as phosphorescent dopants in various concentrations (5–100%) in a N,N′-dicarbazolylbiphenyl (CBP) host. High current efficiency (ηc; up to 125 cd A−1) and power efficiency (ηp; up to 43.6 lm W−1) were observed at appropriate conditions. Because of the steric hindrance of guanidinate ancillary ligands, no significant intermolecular interactions were observed in these complexes, thus leading to the reduction of self-quenching and triplet–triplet (T–T) annihilation at high luminance/currents in OLEDs.

Graphical abstract: Guanidinate ligated iridium(iii) complexes with various cyclometalated ligands: synthesis, structure, and highly efficient electrophosphorescent properties with a wide range of emission colours

Back to tab navigation

Supplementary files

Article information


Submitted
20 Sep 2012
Accepted
30 Oct 2012
First published
30 Oct 2012

J. Mater. Chem. C, 2013,1, 677-689
Article type
Paper

Guanidinate ligated iridium(III) complexes with various cyclometalated ligands: synthesis, structure, and highly efficient electrophosphorescent properties with a wide range of emission colours

V. K. Rai, M. Nishiura, M. Takimoto and Z. Hou, J. Mater. Chem. C, 2013, 1, 677
DOI: 10.1039/C2TC00242F

Social activity

Search articles by author

Spotlight

Advertisements