Efficient synthetic route to anhydrous mononuclear tris(8-quinolinolato)lanthanoid complexes for organic light-emitting devices

A new lanthanoid 8-quinilinolates type structure was found for lanthanum complex La3(qMe)9(H)(NO3) (1) formed in the reaction of La(NO3)3 · 6H2O with 2-methyl-8-hydroxyquinoline (HqMe) and aqueous ammonia in methanol. The molecule of 1 contains three La atoms connected by six bridging quinolinolate ligands, two terminated η2-coordinated qMe ligands, one terminated η1-coordinated qMe ligand and one terminated NO3 group. The geometry and 1H NMR spectrum of the complex suggest that it is bearing −1 charge balanced by proton, which was localized objectively. The arrangement of the compound in crystalline state and in pyridine solution is discussed. Syntheses of water- and acid residual-free mononuclear lanthanoid quinolinolates La(qMe)3(py)2 (2) and Lnq3(py)2, (Ln = Y (3), La (4), Sm (5), Eu (6), Tb (7), Er (8), Tm (9); q = 8-quinolinolate, py = pyridine) by the reaction of appropriate amido complexes Ln[N(SMe3)2]3 with 3 equiv. of 2-methyl-8-hydroxyquinoline or 8-hydroxyquinoline in pyridine solution is also described. The complex Laq3(Ph3PO)2 (10) was prepared by treatment of 4 with triphenylphosphine oxide in pyridine solution. Lanthanum 2 complex revealed photoluminescence intensity ca. 3 × 103 times higher than that of the compound 1 prepared by the traditional way in water–alcohol medium. These data give a ground to consider the Lnq3(py)2 complexes as promising material for design of light-emitting devices.