Phosphorescent heteroleptic iridium(III) cyclometallates: Improved syntheses of acetylacetonate complexes and quantum chemical studies of their excited state properties

Robert D. Sanner, Nerine J. Cherepy, Hung Q. Pham, Victor G. Young

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Abstract

We have investigated methods to prepare cyclometallated iridium(III) complexes with efficient photoluminescence spanning a broad color palette. In particular, we find that addition of ancillary ligands to chloro-bridged iridium dimers proceeds cleanly in refluxing 1,2-dimethoxyethane (DME) without the need for additional product purification. This represents an improvement over the conventional use of 2-ethoxyethanol which requires column chromatographic separation. Our efforts in this work have focused on acetylacetonate complexes such as (F2ppy)2Ir(acac), where F2ppy = 2-(4′,6′-diflurophenyl)pyridinato. We have prepared fifteen compounds by the route, eight of which are newly reported; in four cases we were able to prepare complexes which were inaccessible via the conventional route. Nine of the complexes were characterized by single crystal x-ray diffraction and possess the same distorted octahedral geometry around the iridium with two bidentate phenylpyridine ligands and one bidentate acetylacetonate ligand. Seven of the complexes exhibited efficient photoluminescence with colors ranging from yellow to blue and quantum yields of 0.51–0.74. All of the compounds with trifluoromethyl or phenyl substituents on the acetylacetone displayed emission in the orange with low quantum efficiency. The use of TD-DFT calculations, along with natural transition orbitals (NTOs), permitted a detailed interpretation of the electronic structures for the complexes. The nature of the acceptor orbitals for the low energy triplet state NTOs proved to be an important predictor for the emission spectra of the compounds.

Original languageEnglish (US)
Article number114256
JournalPolyhedron
Volume176
DOIs
StatePublished - Jan 15 2020

Bibliographical note

Funding Information:
We would like to thank Prof. Laura Gagliardi ( University of Minnesota ) for helpful discussions on the quantum chemical calculations. Work at Lawrence Livermore National Laboratory was performed under the auspices of the U.S. DOE under Contract No. DE-AC52-07NA27344 and was supported by the U.S. DOE National Nuclear Security Administration , Defense Nuclear Nonproliferation Research and Development under Contract No. DE-AC03-76SF00098. We thank the X-Ray Crystallographic Laboratory, LeClaire-Dow Instrumentation Facility, Department of Chemistry, University of Minnesota, for its contribution. The authors would like to acknowledge Mr. James T. Moore and the X-Ray Crystallography course CHEM5755 for assistance in collecting single-crystal diffraction data on several complexes presented herein. The Bruker AXS D8 Venture diffractometer was purchased through a grant from NSF/MRI (#1229400) and the University of Minnesota. The computational part of this research (H.P.) was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences under Award DE-FG02-17ER16362. The authors acknowledge the Minnesota Supercomputing Institute (MSI) for providing computing resources. Appendix A

Funding Information:
We would like to thank Prof. Laura Gagliardi (University of Minnesota) for helpful discussions on the quantum chemical calculations. Work at Lawrence Livermore National Laboratory was performed under the auspices of the U.S. DOE under Contract No. DE-AC52-07NA27344 and was supported by the U.S. DOE National Nuclear Security Administration, Defense Nuclear Nonproliferation Research and Development under Contract No. DE-AC03-76SF00098. We thank the X-Ray Crystallographic Laboratory, LeClaire-Dow Instrumentation Facility, Department of Chemistry, University of Minnesota, for its contribution. The authors would like to acknowledge Mr. James T. Moore and the X-Ray Crystallography course CHEM5755 for assistance in collecting single-crystal diffraction data on several complexes presented herein. The Bruker AXS D8 Venture diffractometer was purchased through a grant from NSF/MRI (#1229400) and the University of Minnesota. The computational part of this research (H.P.) was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences under Award DE-FG02-17ER16362. The authors acknowledge the Minnesota Supercomputing Institute (MSI) for providing computing resources.

Keywords

  • Cyclometallated iridium synthesis
  • DFT calculations
  • OLED
  • Phosphorescent iridium complex
  • Photoluminescence

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