Synthesis And Properties Of Cationic Cyclometalated Platinum (Ⅱ) Complexes

Platinum（Ⅱ）complexes have wide phosphorescence emission and long luminescence lifetime,and have shown important applications in the fields of dye-sensitized solar cells and oxygen sensing.So far,platinum（Ⅱ）complexes for luminescent oxygen sensing are mostly neutral complexes,and cationic platinum（Ⅱ）complexes have been reported relatively rarely for luminescent oxygen sensing.The principle of luminescence oxygen sensing is to use molecular oxygen to quench the phosphorescences（or delayed fluorescences）of oxygen-sensitive probes（OSPs）to achieve the detection of oxygen concentration.As a kind of phosphorescent materials,the luminescence of cationic cyclometalated platinum（Ⅱ）complexes can also be quenched by molecular oxygen.Therefore,investigation of the structure-property relationship between the structures of the cationic cyclometalated platinum（Ⅱ）complexes and their oxygen sensitivity is of great significance for the development of new OSPs.Platinum（Ⅱ）complexes with a planar quadrilateral structure usually encounter“Aggregation-caused quenching（ACQ）”,which limits strongly their uses in many fields.Therefore,the design and development of platinum（Ⅱ）complexes with anti-ACQ effect（Aggregation-induced phosphorescent emission,AIPE）has become a research hotspot in recent years.In this thesis,the main research content includes the following two parts.1.Six new cationic cyclometalated platinum（Ⅱ）complexes Pt1-Pt6 were designed and synthesized.Among them,complexes Pt2-Pt6 are modified with a diphenylamino group.The photophysical,electrochemical properties and oxygen sensitivity of these platinum（Ⅱ）complexes were investigated systematically.It is found that the introduction of different groups at the 5-position of the pyridine ring of the cyclometalated ligand2-（4-diphenylamino）phenylpyridine can tune the maximum emission wavelength of the cationic cyclometalated platinum（Ⅱ）complexes in the range of 544 nm to 611 nm.The oxygen sensing results show that Pt5 with a trifluoromethyl group at the 5-position of the pyridine ring demonstrates the highest oxygen sensitivity,and its I₀/I_2.17(I₀ represents the phosphorescence intensity of the complexes under a 100%nitrogen atmosphere,and I_2.17represents the phosphorescence intensity of the complexes at a volume fraction of oxygen of2.17%)value in DMF solution is 6.4,I₀/I₁₀₀(I₁₀₀ represents the phosphorescence intensity of the complexes at a volume fraction of oxygen of 100%)was 49.2.2.Four new cationic cyclometalated platinum（Ⅱ）complexes Pt7-Pt10 with AIPE properties were designed and synthesized,and their photophysical and electrochemical properties were studied.The results show that complexes Pt7-Pt10 are AIPE-active,and their absolute quantum yields in the H₂O/DMF solution increase clearly with the increase of water content.Transmission electron microscope（TEM）results show that the complexes Pt7-Pt10were aggregated into nanofibers or dendritic structures in H₂O/DMF solution at a 90%water content.