Air stable and efficient rare earth Eu(II) hydro-tris(pyrazolyl)borates complexes with tunable emission color
Luminescent rare earth Eu(II) complexes with characteristic 5d-4f transition show potential in various applications. However, the exploration and further application of typical Eu(II) complexes are strongly impeded by their instability arising from the easily oxidation of Eu2+ ions. In this work, three new Eu(II) complexes bis(hydro-tris(3-phenyl-5-methylpyrazolyl)borates)europium(II) (Eu(TpPh,Me)2), bis(hydro-tris(3-phenylpyrazolyl)borates)europium(II) (Eu(TpPh)2), and bis(hydro-tris(3,5-diphenylpyrazolyl)borates)europium(II) (Eu(TpPh2)2) were designed and synthesized. Their crystal structures, photophysical properties and air stabilities were characterized and discussed. It is found that the introduction of bulky phenyl group not only increases the air stability by sterically hindering the central Eu2+ ions, but also tunes the maximum emission wavelength by influencing the crystal field. This work provide rules for regulating luminescence properties of Eu(II) complexes as well as design basis for achieving stable and efficient Eu(II) complexes.
- This article is part of the themed collections: Celebrating 110 Years of the College of Chemistry and Molecular Engineering of Peking University and Rare Earth Chemistry – In memory of Professor Xu Guangxian at his centenary