Synthesis, quantum chemical calculations, and luminescent properties of scandium, europium, gadolinium, and terbium 1-(2-pyridyl)naphtholate complexes

By reactions of 1-(2-pyridyl)naphth-2-ol (pynH) with silylamides Ln[N(SiMe3)2]3 (Ln = Sc, Eu, Gd, or Tb), the Ln(pyn)3 complexes of the metals have been synthesized. Only the scandium complex in a THF solution has displayed photoluminescence (band with a maximum at 455 nm and a halfwidth of 65 nm). Electroluminescent properties have been revealed for the scandium and terbium complexes. In an ITO/TPD/Sc(pyn)3/Bath/Yb three-layer light emitting diode, the scandium complex exhibits yellow-green luminescence with a brightness of 4750 cd/m2 at a voltage of 21 V. The terbium complex Tb(pyn)3 in the same device has displayed a single, broad luminescence band with λmax = 570 nm due to excimer emission. By density functional theory quantum chemical calculations, different structures of the complexes have been revealed, mononuclear for Sc(pyn)3 and binuclear for Ln2(pyn)6. This difference in structure seems to be responsible for differences in electroluminescent activity between the synthesized complexes.