Synthesis And Properties Of Cyclometalated Ir(?) Complexes With A 2,2'-Bipyridine Ligand

Iridium(?)complexes demonstrate strong phosphorescence emission and long luminescence lifetime,and have shown important applications in the fields of luminescent oxygen sensing and aggregation-induced phosphorescent emission(AIPE)materials.So far,the phosphorescent materials used as luminescent oxygen sensitive probes(OSPs)are mostly ruthenium(?)complexes,platinum(?)or palladium(?)porphyrin complexes.However,there are relatively few reports on the fluorinated cationic cyclometalated Ir(?)complexes as OSPs based on 2,2'-bipyridine ancillary ligand.The principle of luminescent oxygen sensing technology is based on the quenching of the phosphorescence of OSPs by oxygen molecules to achieve the detection of oxygen concentration.Therefore,studying the relationship between the structure-property of fluorinated Ir(?)complexes is of great significance for constructing novel OSPs with excellent performance.On the other hand,the octahedral configuration of most Ir(?)complexes is difficult to achieve metal-metal stacking,and usually encounters "aggregation-caused quenching(ACQ),which limits the application of Ir(?)complexes as solid phosphorescent materials.Therefore,the development of AIPE-active Ir(?)complexes is of great importance.Thus,the main research contents of this thesis include the following three parts.1.Six cationic cyclometalated Ir(?)complexes Ir0-Ir5 containing a 2,2'-bipyridine ancillary ligand were designed and synthesized.Among them,complexes Irl-Ir5 are modified with fluorine atoms.The influences of the number and the position of fluorine atoms at the cyclometalating ligands on the photophysical,electrochemical and oxygen sensing properties of the Ir(?)complexes have been investigated systematically.The results show that the introduction of fluorine atom on the 2-phenylpyridine ligand blue-shifts the maximum emission wavelength,increases the photoluminescence quantum yield and prolongs the phosphorescence lifetime(for instance,Ir4:?em=514 nm,?PL=50.8%,?=1.29?s).And as the number of fluorine atoms increases,the same effects mentioned-above are also observed.Oxygen sensitivity test results show that these complexes can monitor the oxygen concentrations within a wide range in real-time.2.Four new cationic cyclometalated Ir(?)complexes Ir6-Ir9 containing a 2,2'-bipyridine ancillary ligand were designed and synthesized,and their photophysical and electrochemical properties were studied.The results show that the complexes Ir7 and Ir8 are AIPE-active.Their single crystal structures show that the unique intermolecular "?-? clamp interlock" structure is a key parameter for the AIPE performances of Ir7 and Ir8.Introducing a fluorine atom into the 5-position of the pyridine ring of the cyclometalating ligand to construct intermolecular C-H…F hydrogen bonds can significantly enhance the AIPE performance of Ir8.Moreover,transmission electron microscopy(TEM)and confocal laser scanning microscopy(CLSM)tests showed that regular nanosheets were formed by the aggregation of complexes Ir7 and Ir8 at a water content of 90%in CH3CN/H2O solution,respectively.3.Four new cationic cyclometal Ir(?)complexes Ir10-Ir13 containing a 2,2'-bipyridine ancillary ligand were designed and synthesized.These complexes show tipycal intermolecular"?-? clamp interlock" structure.Among them,Ir10,Ir12 and Ir13 are AIPE-active.Through in-depth investigation on their single crystal structures and intermolecular interactions,the reason why the complexes Ir10,Ir12 and Ir13 are AIPE-active is explained.Moreover,the emission performance of the Ir(?)complexes can be regulated by different intermolecular C-H…F hydrogen bonds.