Construction And Application Of Cationic Metal Iridium(?) Complexes

In recent years,Ir(?)complexes have exhibited the potential application prospects in the fields of electroluminescence devices,chemosensors,photocatalytic water reduction and biological imaging because of their advantages of easy tunability of the emission wavelength as well as photo-and thermal stabilities.However,there are two serious problems for the practical application of Ir(?)complexes:(1)Ir(?)complexes usually suffer from the aggregation-caused quenching(ACQ)in the solid or aggregation state,resulting from the interaction between closely packed molecules,which limits the practical application of these materials.(2)The structure-property correlations of Ir(?)complexes are largely unexplored,which hinders the application of Ir(?)complexes in different fields.Therefore,the development of high-performance Ir(?)complexes is the focus of related work.In 2001,Tang et al.first reported the phenomenon of aggregation-induced emission(AIE),which is the opposite of ACQ.At present,the research on small organic molecules with AIE properties has developed rapidly.However,the cationic Ir(?)complexes possessing AIE properties are rarely reported.Therefore,the design and synthesis of such materials with AIE properties are beneficial for achieving highly efficient solid-state luminescence.Moreover,it is still the focus of related work to explore the structure-property correlations and achieve the adjustment of photophysical,electrochemical properties of corresponding complexes through the effective molecular construction,and further realize the better application of such complexes.According to these theoretical basis,two types of functional cationic Ir(?)complexes have been constructed by the choice and variation of cyclometalated and ancillary ligands,and their photophysical and electrochemical properties are studied in detail.The applications of these two types of complexes in data recording,volatile organic compounds detecting and photocatalytic hydrogen generation fields are explored.The details are as follows:(1)Through the modification of pyridine-1,3,5triazine,two cationic Ir(?)complexes with AIE and piezochromism properties were constructed in the absence of soft substituents,such as imine units,flexible alkyl chains and dendrimer-like.Based on the ~1H NMR,PXRD and DFT experiments,the behaviour of AIE and piezochromism of these two complexes are ascribed to the restriction of intramolecular motion and the transformation between crystalline state and amorphous state,respectively.And we hope this molecular design can provide a new strategy for developing materials with AIE and piezochromism properties.It is displayed that these two complexes provide the data recording and volatile organic compounds detecting devices,showing the potential application of these complexes.(2)A series of cationic Ir(?)complexes was designed and constructed by introducing an ancillary ligand with formyl group,and the photophysical and electrochemical properties of these complexes were adjusted successfully by the selection of cyclometalated ligands.These new complexes were assessed as photosensitizers(PSs)under the system of photocatalytic hydrogen generation.The formyl groups can make PSs absorb on the surface of colloidal platinum,which is beneficial to accelerate electron transfer between PSs and catalysts,thereby improving the activity of photocatalytic hydrogen generation.Moreover,the structure-activity correlations of PSs are fully explored by analyzing the processes of light absorption,charge separation and electron transfer,which provides a research basis for the design and synthesis of highly efficient and stable PSs in the future.