Synthesis and Characterization of Oxazaborinin Phosphonate for Blue OLED Emitter Applications

• Published in: Chemphyschem Vol. 20; no. 5; pp. 665 - 671
• Main Authors: Köhling, Jonas, Kozel, Volodymyr, Jovanov, Vladislav, Pajkert, Romana, Tverdomed, Sergey N., Gridenco, Oleg, Fugel, Malte, Grabowsky, Simon, Röschenthaler, Gerd‐Volker, Wagner, Veit
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 04.03.2019
• Subjects: Boron; Coordination compounds; difluoroboronic compound; Emitters; fluorescence; Ligands; materials science; Molecular orbitals; N,O ligands; Organic light emitting diodes; Phenols; Phospho-Fries rearrangement; Photoluminescence; Synthesis; Thermal stability; Vacuum deposition; Fluorescence; Phospho-Fries rearrangement; N,O-difluoroboronic compound; materials science
• ISSN: 1439-4235; 1439-7641
• DOI: 10.1002/cphc.201801087

A blue‐light emitting material based on a boron complex containing heteroaromatic phosphonate ligand is synthesized and characterized. The Phospho‐Fries rearrangement is used in the synthesis route of the ligand as a convenient method of introducing phosphonate groups into phenols. Structural, thermal and photophysical properties of the resulting oxazaborinin phosphonate compound have been characterized. DFT geometry optimizations were studied as well as the spatial position and symmetry of the HOMO and LUMO. Good thermal stability up to 250 °C enables vacuum deposition methods next to solution processing. Combining the work function with the optical band gap from UV‐Vis measurements shows that band alignment is possible with standard contact materials. Photoluminescence reveals an emission peak at 428 nm, which is suitable for a blue light‐emitter. Shining blue: A new oxazaborinin phosphonate compound suitable for OLED applications is synthesized by Phospho‐Fries rearrangement. HOMO and LUMO orbitals have fluorescence allowed symmetry with good overlap. The bulky phosphonate group reduces π–π‐stacking in solid phase. Structural, thermal and photophysical properties are characterized of solution processed samples and vacuum deposited thin layers. Photoluminescence occurs at 428 nm, which is suitable for a blue light‐emitter.