Synthesis and Luminescent Properties of a Series of Polymeric Metal Complexes from Nitrogen-/Oxygen Containing Rigid Ligands
|Keywords||Polymeric Metal Complexes Self-assembly Conductivity Fluorescent Properties|
Electroluminescence is a physical phenomenon which the electricity energy was directly transformed into ray radiation. Electroluminescent materials include inorganic and organic luminescent materials. Inorganic electroluminescence materials have many shortcoming, such as the low luminescent efficiency, high driving voltage, radiation, difficult process, difficultly forming membrane, so they are difficult to form great area display. Organic luminescent materials include organic complexes, metal coordination complexes and organic macromolecules. Among them, the luminescent properties and efficiency of metal coordination complexes are higher, and they have also good resolvable. But the hot stability, forming membrane and process of the metal coordination complexes are not as good as organic macromolecules, however, the luminescent efficiency of the organic macromolecule electroluminescent materials and the quanta efficiency of the corresponding to diodes are not as good as metal coordination complexes in despite of having high hot stability and good forming membrane, so it is a hot research field to exploit excellent luminescent materials which possess both high luminescent efficiency、quanta efficiency and high hot stability、chemical stability and good forming membrane、process now.The main chain polymeric metal complexes are formed by self-assembly through coordination bonds between bidentate or multbentate organic ligands and central metal ions, polymeric metal complexes not only possess the high hot stability and good forming membrane of the organic macromolecules, but also possess the excellent luminescent properties of the metal coordination complexes, so the studies of polymeric metal complexes as excellent electroluminescent materials have great potential and significance now.Based on the principle, we selected two rigid N,N-containing ligand and N,O-containing ligand and obtained four novel polymeric metal complexes under the solution conditions by self-assembly in this paper, and then measured their luminescent properties. The main contents are following:1.Choose an appropriate synthesis route, a N,N rigid ligand: 1,4-bis([1,10]phenanthroline-[5,6-d]imidazol-2-yl)benzene (BPIB) (1)and a N,O rigid ligand: 4,4’-bis(8-hydroxyquinoline-5-propenyl)-biphenyl (B8QPB) (1)have been synthesized. The two ligands have been characterized by IR, NMR and elementary analysis.2.Ligand BPIB reacts with copper ion or zinc ion, and ligand B8QPB reacts with aluminum ion or zinc ion, respectively, four new polymeric metal complexes have been synthesized, BPIB-Cu(Ⅱ) (2),BPIB-Zn(Ⅱ) (3), B8QPB-Al (Ⅲ) (2) , B8QPB-Zn (Ⅱ) (3) have been primary characterized by IR, elementary analysis, conductivity measurements, gel permeation chromatography (GPC) and thermal gravimetric analysis (TGA). The results of experiment indicate that the ligands are successly coordinated with metal ions and form polymers, the degrees of polymerization (n) are 7, 7, 11,32 for four polymers, and their molecular formula is [(C32H18N8)7(CuCl2)8], [(C32H18N8)7(ZnCl2)8],[(C34H24O2N2)11Al12Cl28], [(C34H24O2N2)32(ZnCl2)33], respectively.3.Using Ultraviolet-visible (UV-vis) spectra and Perkin-Elmer LS55 luminescence spectrometer, their fluorescence properties in solid state and in solution state have been researched. The differences of between ligands and some metal ions have been compared. From the results of emission spectra, BPIB-Cu(Ⅱ)(2)、BPIB-Zn(Ⅱ)(3) emit purple/blue light in 423nm and 434nm in solution state, and the two polymeric metal complexes emit blue/green light in 526nm and 517nm in solid state, respectively; B8QPB-Al (Ⅲ)(2)、B8QPB-Zn (Ⅱ)(3) emit blue/green light in 507nm and 470nm in solution state,and the two polymeric metal complexes also emit blue/green light in 507nm and 514nm in solid state, respectively. The results of thermogravimetric analyses indicate that they have good thermal stability, which the char yields % is large 55 wt%; the glass-transition temperature (Tg) of BPIB-Cu(Ⅱ) (2) and BPIB-Zn(Ⅱ) (3) is large 232℃, the glass-transition temperature (Tg) of B8QPB-Al (Ⅲ) (2) and B8QPB-Zn (Ⅱ) (3) is large 167℃, respectively. Polymeric metal complexes have good emission properties and high thermal stabilities which have potential as excellent electroluminescent materials, and the electroluminescent properties of the novel polymeric metal complexes are under investigating.