Synthesis and luminescence properties of lithium, zinc and scandium 1-(2-pyridyl)naphtholates

1-(2-Pyridyl)naphth-2-ol (pynH) was synthesized from 2-bromopyridine and 1-bromo-2-hydroxynaphthalene and structurally characterized. This ligand and the known 2-(2-pyridyl) phenol (ppH) ligand were reacted with LiN(SiMe3)(2), ZnEt2 and Sc[N(SiMe3)(2)](3) to prepare the new luminescent complexes Li(pp), Li(pyn), Zn(pyn)(2), Sc(pp)(3), Sc(pyn)(3) and known Zn(pp)(2). Photoluminescent (PL) spectra of the compounds contained a single broad band with a maximum at 447-473 nm. The OLED devices with a configuration of ITO/TPD/complex/Bath/Yb gave blue-green emission. The emission spectra of these devices resembled the PL spectra; however, the bands of electroluminescence (EL) were shifted 20-40 nm to the long-wavelength side. A maximum current efficiency 15.3 cd/A and a power efficiency 8.12 lm/W at 100 cd/m(2) were measured for the device with the zinc luminophore Zn(pp)(2), whereas the highest luminance of 8300 cd/m(2) at 22.5 V was observed with the device with the scandium complex Sc(pp)(3). DFT calculations showed that the latter complex exhibited the lowest HOMO and the highest LUMO energy levels compared with the other investigated compounds. The calculated trends with respect to the influence of the metal and the ligand on the LUMO-HOMO gap agree well with the shifts of the electronic transitions observed in the PL spectra of the complexes. (C) 2012 Elsevier B.V. All rights reserved.