Studies On Syntheses, Characterization, Luminescent Properties Of Metal Complexes With Imine Ligands

Luminescent coordination compounds have been one of the most active researchareas because of their potential application in light emitting diodes (LEDs). Themetal complexes with nitrogen-containing ligands have been synthesized and theirluminescent behavior studied. The change of center metal ion, the size ofπ-conjugated system of the ligand and the electronic effect of substituents on theligand are important factors for modulating its luminescent properties. The frequencyand intensity of the luminescence of the complex are modulated via the design of theligand-modified and center metal, so that luminescent properties are improved basedon metal coordination compounds.Our research results indicate that the new chelating bidentate anilido-imineconjugated ligands are well suited for synthesizing the four-coordinate alkylaluminum complexes by alkane elimination reaction of AlMe3 with correspondingligands at room temperature. 1H and 13C NMR spectra reveal that these aluminumcomplexes have Cs-symmetric structures in solution and X-ray diffraction analysisindicates that the six-membered chelating ring in these complexes is nearly planarwith the aluminum lying slightly out of the plane. These new complexes producebright fluorescence in both solution and the solid state, and the emission color insolution can be tuned by the ortho substituents on the rotatable aryl rings of theligands.We also prepared the four-coordinate aluminum complexes by a salt metathesisreaction of AlCl3 with the lithium salt of corresponding ligands at room temperature.1H and 13C NMR spectra reveal that these aluminum complexes have Cs-symmetricstructures in solution and X-ray diffraction analysis indicates that the six-memberedchelating ring in these complexes is nearly planar with the aluminum lying slightlyout of the plane. These complexes produce bright fluorescence in both solution andthe solid state. The quantum yields of these compounds are lower than correspondingalkyl aluminum complexes in solution, due to the heavy atom effect of chlorine.Three novel dinuclear dialkylaluminum complexes was designed and synthesized,their photophysical and electroluminescent properties have been studied. First usingthis strongly (Φf = 0.30) fluorescent four-coordinate aluminum complex 3a as adopant, the charge trapping, and likely combined with F?rster transfer is thedominant EL mechanism in single layer polymer light-emitting devices withPVK-PBD (40 wt.-%) as host. Then doping concentration 0.5 wt.-%, single layerpolymer light-emitting device achieved a maximum current efficiency of 3.2 cd A-1.Our preliminary results demonstrate that high-efficiency light-emitting devices canbe realized with polymers a host and complex 3a as guest, and that these devices canbe fabricated by processing the luminescent layer from solution. The white organiclight-emitting devices (WOLEDs) also have been fabricated. The devices structure isas follows: ITO/PEDOT:PSS/3a:PF:PVK/Ba/Al. A fairly pure WOLED with CIEcoordinates of (0.32, 0.33) at 100 cd/m2 is realized when PVK: PF = 10:1 and 3a:PF(wt %) = 0.06, and device achieved a maximum current efficiency of 0.6 cd A-1.We have prepared via C–H bond activation and structurally characterized the firstexample of hitherto unknown dialkylaluminum pincer complexes. We also studiesthe reaction mechanism. The crystal structure analysis reveals that the pincercomplex is five-coordinate and adopt distorted trigonal bipyramidal geometry formetal center. This method can also be applied for other main-group metal pincercomplexes.At last, we have described the syntheses and X-ray structure of d10 complexessupported by two substituted 2, 2`-bipyridine ligands. Crystal structure analysisreveal crystal structures of these complexes are different each other. In complexes 2aand 2c, π–π staking forming antiparallel dimer structures. In contrast, there areone-dimensional supramolecular structures via intermolecular interactions incomplexes 2b and 2d in the solid state. These complexes produce bright fluorescencein both solution and the solid state, and the emission color in the solid state can betuned by the ligands or center metal. The d10 complexes with substituted 2,2`-bipyridine ligands are a new class of luminescent material with potentialapplications in optoelectronic devices.