Synthesis And Properties Of Luminescent Metallomesogens Based On Iridium And Platinum

Luminescent liquid crystal materials have very important application in organic electroluminescent diodes due to their unique photophysical property and fluidity of liquid crystals.However,most of the reported luminescent liquid crystal materials are fluorescent materials which has the theoretical internal quantum efficiency of 25%.Compared with fluorescent materials,the phosphorescent materials based on cyclometallated iridium and platinum complexes have a 100%theoretical internal quantum efficiency.Therefore,the phosphorescent metallomesogens have attracted much attention by the researchers.In this thesis,we mainly focused on the phosphorescent liquid crystal materials bearing transition metal atom.With this in mind,the iridium and platinum complexes based metallomesogens were designed and synthesized,and the structure-property relationship of these molecules were discussed.The main contents of this thesis are as follows:1. A class of luminescent metallomesogens of Ir1,Ir2,Pt1 and Pt2 were designed and synthesized,in which the gallic acid derivatives were used as mesogenic moiety,amides and ester groups as linker units and cyclometalated iridium/platinum complexes as emission core.The molecular structures were confirmed by ¹H NMR,¹³C NMR and MALDI-TOF MS.The photophysical,electrochemical,thermodynamic and liquid crystal properties of the iridium/platinum complexes were investigated by UV-vis absorption spectrum,fluorescence spectrum,cyclic voltammetry,thermogravimetry,differential scanning calorimetry and polarized optical microscopy.The solution-processable OLEDs based on these cyclometalated iridium/platinum complexes were fabricated and the electroluminescent properties were explored.The results showed that the complexes with amide linker exhibited a better thermal stability and a higher phase transition temperature,concomitant with the red-shifted absorption and emission spectra.The complexes Ir1,Ir2,Pt1 and Pt2 showed the maximum emission wavelength of 513,544,521 and 541 nm in solution,respectively.The devices presented the emissive peaks at 508,521,516 and 539 nm for complex Ir1,Ir2,Pt1 and Pt2,respectively.The corresponding CIE coordinates are?0.26,0.62?,?0.30,0.64?,?0.26,0.50?and?0.32,0.58?,which belongs to green light emission.2. A series of cyclometalated platinum complexes-based metallomesogens,named Pt1,Pt2 and Pt3,were synthesized,in which the tetraphenylethene and alkyl chains were introduced into the cyclometalating ligand?2-phenylpyridine?and the biphenyl mesogenic group was integrated into the ancillary ligand?acetylacetone?.Their molecular structures were confirmed by ¹H NMR,¹³C NMR and MALDI-TOF MS.The photophysical,electrochemical,thermodynamic and liquid crystal properties of the platinum complexes were investigated by UV-vis absorption spectrum,fluorescence spectrum,cyclic voltammetry,thermogravimetry,differential scanning calorimetry and polarized optical microscopy.The solution-processable OLEDs based on these cyclometalated platinum complexes were fabricated and the electroluminescent properties were explored.The research results demonstrated that the length of the alkyl chain has a great influence on the thermal stability and phase transitions rather than the photophysical property.The maximum emission wavelengths of Pt1,Pt2 and Pt3 were 536,534 and 536 nm respectively.The solution-processable OLEDs based on Pt2 and Pt3 displayed the emission peaks at530 nm,and the CIE coordinates are?0.30,0.41?and?0.33,0.50?respectively,ascribing to green light emission.The external quantum efficiency of the Pt2 and Pt3-based devices were 0.15%and 0.50%respectively.