The Research Of Structures And Luminescence Properties On Cu(I) Complexes For OLED

Nowadays organic light emitting device(OLED) has been more widely used, and in which the light-emitting materials have been recieved more and more attention. Compared to other metal in other luminescent complexes, copper exhibits many advantages that it is cheap, environment friendly, non-toxic and so on, and the copper reserves of China is rich, ranking the third in the world. Similar to the Ir complexes, Cu(I) complexes as phosphorescent material used in OLED also have maximum IQE in theory, arousing people to research the Cu(I) complexes. Many studies have achieved the desired emission through the modification of the ligand and adjust the molecular structure. In this thesis, two methods of solution method at room temperature and solvothermal method have been used to obtain a series of Cu(I) complexes. On this basis, the properties and the crystal structures of these compounds have been further investigated to reveal the relationships between the structures and properties. The specific contents are as follows:1. Benzoxazole Complexes: based on the literature reviews, three kinds of benzoxazole derivatives have been synthesized: 2-PBO, 4-Me-2-PBO, 2-QBO, and series of complexes 1-8 have been successfully synthesized. We use single-crystal X-ray diffraction to studied their crystal structures. All complexes have been characterized as ionic mononuclear complexes. It has been found that 2-QBO complexes exist phase transition due to its dihedral change, leading to allomorphic type complexes 5-7. Every phase can be reversed to each other using different process solvents. Complexes 1-8 show different luminescent properties. In comparison to other 2-PBO complexes 1-3 and 4-Me-2-PBO complex 4, the emission intensity of 2-QBO complexes is significantly higher. The UV-Vis absorption showed that all transitions are MLCT character.2. Halogen and mixed-halogen binuclear complexes based on the POP ligand, [Cu(POP)Cl]2 [9], [Cu(POP)Br]2 [10], [Cu(POP)I]2 [11], [Cu(POP)]2Br Cl [12]. Four complexes have been characterized as similar structures in which Cu2X2 cores are bridged by the POP ligand to form dinuclear structrues. They show strong light emitting from the(M + X) LCT excited states, and a small redshift in the emiting wavelength can be observed due to different polarization rates of halogen(Cl- <Br-<I-). A energy reduction in the emission is found in the mixed-halogen complex 12 due to the break in the symmetry of the entire structure of cluster molecules caused by the presence of different halogen atoms,.3. The mononuclear and polynuclear complexes 13-15 based on the ligand dppy. Complex 13 characterized as a dinuclear structure formed by the bridged ligand dppy and Cu2I2 core, complexes 14 characterized as a trinuclear structure formed by the bridged dppy and Cu3I2 core. The complex 15 consists of two separate mononuclear molecules. The UV-Vis absorption spectra of complex 13 and 14 show strong(M + X) LCT transitions and complex 15 shows a strong MLCT transition. Because of the influence of the structural rigidity, complex 13 has yellow green luminescence and complexes 14 and 15 show green luminescence. 14 have a little redshift in emission than 15. Thermal analysis shows that all complexes are stable.4, A series of Zn(II) complexes which are also d10 element like Cu(I) coordinated with 4-PBO ligand have studied. The specific structures and properties of complexes 16-18 which are coordinated with halogen ligand have been obtained and with the nitrate ligand 19 also achieves. Since the π-π stacking interactions and hydrogen bonding interactions, all complexes easily form supramolecular chains. The electronic absorption spectrum shows strong ILCT transfer characteristics. Halogen-containing complexes 16-18 are in 350-600 nm with strong luminescence, and complex 19 has a large redshift with the band of 375-650 nm. Different halogen complexes also exist redshift phenomenon due to ligand field strength(I- <Br- <Cl-) and steric hindrance called Jahn- Teller distortion. Thermal analysis also shows the good thermal stability of all complexes for the manufacture of light-emitting device.