Syntheses, structures, and electroluminescence of new blue/green luminescent chelate compounds: Zn(2-py-in)(2)(THF), BPh2(2-py-in), Be(2py-in)(2), and BPh2(2-py-aza) [2-py-in=2-(2-pyridyl)indole; 2-py-aza=2-(2-pyridyl)-7-azaindole]

Four novel blue/green luminescent compounds, Zn(2-py-in)(2)(THF) (1), BPh2( 2-py-in) (2), Be(2-py-in)(2) (3), and BPh2(2-py-aza) (4), where 2-py-in = 2 -(2-pyridyl)indole and 2-py-aza = 2-(2-pyridyl)-7-azaindole, have been synt hesized and fully characterized. The 2-py-in ligand and 2-py-aza ligand in the new compounds are chelated to the central atom; Compounds 2-4 are air s table and readily sublimable, with a melting point above 250 degrees C. In the solid state, compounds 1-4 have an emission maximum at lambda 488, 516, 490, and 476 nm, respectively. The structures of compounds 2 and 4 are sim ilar. The blue shift of emission energy displayed by compound 4, in compari son to that of 2, is attributed to the presence of an extra nitrogen atom i n the 2-py-aza ligand as confirmed by ab initio calculations on compounds 2 and 4. Electroluminescent devices of compounds 3 and 4 were fabricated by using N,N'-di-1-naphthyl-N,N'-diphenylbenzidine (NPB) as the hole transport ing layer, Alq(3) (q = 8-hydroxyquinolato) as the electron transporting lay er, and compound 3 or 4 as the light emitting layer. At 20 mA/cm(2) the EL device of 3 has an external efficiency of 1.06 cd/A while the EL device of 4 has an external efficiency of 2.34 cd/A, demonstrating that compounds 3 a nd 4 are efficient and promising emitters in electroluminescent devices.