Syntheses, Luminescent/Electroluminescent Properties And Quantum Chemistry Theoritical Studies Of Bis (salicyladimine) Complexes

Recently, Schiff base complexes have attracted much attention with their synthesis,structure and calalyze properties. Bis(salicyladimine) complexes are also good tridentateN-donating ligands with large π-conjugating system, they should be good luminescentcompounds. However, little reports on the luminecent properties of these ligands and theircomplexes hase been found, we are very interested in the luminescent properties of thesecompounds. There are difficult to gain the crystal of Schiff base and Schiff base complexes.Now little reports on the crystal of these ligands and their complexes hase beenfound .Through the analysis of crystal structure to illustrate the state in the molecular andconfirm the key factor that effect the charge transport properties of the molecular in solid, it isvery important for the design and synthesis of organic electroluminescent materials with goodcharge transport properties. The change of the size of π-conjugated system of the ligand and the electronic effect ofsubstituents on the ligand are important factors for modulating its luminescent properties. Thefrequency and intensity of the luminescence of the complex are modulated via the design ofthe ligand-modified and center metal, so that luminescent properties are improved based onmetal coordination compounds. Six Bis(salicyladimine) complexes were synthesized. The complexes have luminescenceat room temperature in solution and the solid state. Their fluorescence property has beenstudied and their fluorescence quantum yields have been determined. It is illuminated thatdifferent substituents have different effect on fluorescence quantum yields. Electron-donatingsubstituents improve the fluoresunce quantum yields of Schiff base complexes, whileelectron-withdrawing substituents descend the fluorescence quantum yields of Schiff basecomplexes. It is found that the fluorescent emission of these complexes originates fromligand-centered π-π* transition. The Zn (Ⅱ) centers play a key role in enhancing thefluorescent emission of the ligands. Through the simple double or three layer strurcture, we study the organicelectroluminescent properties of these complexes. We fabricated organic white light-emittingdevices (LEDs) based on the exciplex emission formed at the interface between thehole-transporting layer NPB and the emitting layer and electron-transportinglayer(1,2–cyclohexanediamino-N, N'- bis (salicylidene) zinc. The devices have goodperformance with simple structure and pure colour. The method will be a effect way tofabricatorganic white light-emitting devices (LEDs). Six bis(salicyladimine) –pyridine complexes were synthesized. Four crystal structure ofthese complexes were determined. The complexes are five-coordinated, distorted squarepyramid. There are different molecular interactions in the solid state of these complexes.Complexes have strongly fluorescent emission both in solution and in the solid state at roomtemperature. The fluorescent emission of these complexes originates from ligand-centeredπ-π* transition. The Zn (Ⅱ) centers play a key role in enhancing the fluorescent emission ofthe ligands.Their luminescent properties show that they are a new class of luminescent metalcomplexes with potential applications in OEL devices. The efficiency of organic light-emitting devices were determined by the mechanism of theelectron transition between the ground and excited state. On the basis of the optimizedgeometrical structure, the electronic spectrum properties of the twelve complexes werestudied by time-dependent density functional theory (TD-DFT) via a hybrid functional ofB3LYP and 6-31G(d) basis set. The molecular orbital, electron transition and the character ofthe electronic spectrum were studied. The TD-DFT calculation result is in good agreementwith the experimental values and gives the reason of red-shift in the electronic spectrum.