Role of the Diphosphine Chelate in Emissive, Charge-Neutral Iridium(III) Complexes

Liao, Jia-Ling; Devereux, Leon R.; Fox, Mark A.; Yang, Chun-Chieh; Chiang, Yu-Cheng; Chang, Chih-Hao; Lee, Gene-Hsiang; Chi, Yun

Abstract

A class of neutral tris-bidentate Ir(III) metal complexes incorporating a diphosphine as a chelate is prepared and characterized here for the first time. Treatment of [Ir(dppb)(tht)Cl3] (1) with fppzH afforded the dichloride complexes, trans-(Cl,Cl)[Ir(dppb)(fppz)Cl2] (2) and cis-(Cl,Cl)[Ir(dppb)(fppz)Cl2] (3). The reaction of 3 with the dianionic chelate precursor bipzH2 or mepzH2, in DMF gave the complex [Ir(dppb)(fppz)(bipz)] (4) or [Ir(dppb)(fppz)(mepz)] (5), respectively. In contrast, a hydride complex [Ir(dppb)(fppz)(bipzH)H] (6) was isolated instead of 4 in protic solvent, namely: DGME. All complexes 2 - 6 are luminescent in powder forms and thin films where the dichlorides (2, 3) emit with maxima at 590-627 nm (orange) and quantum yields (Q.Y.s) up to 90% whereas the tris-bidentate (4, 5) and hydride (6) complexes emit at 455-458 nm (blue) with Q.Y.s up to 70%. Hybrid TD-DFT calculations showed considerable MLCT contribution to the orange-emitting 2 and 3 but substantial ligand-centered 3ππ* transition character in the blue-emitting 4 - 6. The dppb does not participate to these radiative transitions in 4 - 6, but it provides the rigidity and steric bulk needed to promote the luminescence by suppressing the self-quenching in the solid state. Fabrication of an OLED with dopant 5 gave a deep blue CIE chromaticity of (0.16, 0.15). Superior blue emitters, which are vital in OLED applications, may be found in other neutral Ir(III) complexes containing phosphine chelates.

Citation

Liao, J., Devereux, L. R., Fox, M. A., Yang, C., Chiang, Y., Chang, C., …Chi, Y. (2018). Role of the Diphosphine Chelate in Emissive, Charge-Neutral Iridium(III) Complexes. Chemistry - A European Journal, 24(3), 624-635. https://doi.org/10.1002/chem.201703482

• Journal Article Type: Article
• Acceptance Date: Oct 12, 2017
• Online Publication Date: Dec 6, 2017
• Publication Date: Jan 12, 2018
• Deposit Date: Oct 16, 2017
• Publicly Available Date: Dec 6, 2018
• Journal: Chemistry - A European Journal
• Print ISSN: 0947-6539
• Electronic ISSN: 1521-3765
• Publisher: Wiley
• Peer Reviewed: Peer Reviewed
• Volume: 24
• Issue: 3
• Pages: 624-635
• DOI: https://doi.org/10.1002/chem.201703482
• Public URL: https://durham-repository.worktribe.com/output/1346364