The Research On The Luminescene Switching Properties Of Platinum(Ⅱ) Complexes Bearing 2-Phenylpyridine Derivatives

The cycloplatinated（Ⅱ） complexes have important application prospects in many fields such as high-efficiency luminescent display materials,electroluminescent devices,and biological imaging systems due to their high-efficiency phosphorescence caused by strong coordination field effect and spin-orbit coupling.For a long time,the researches on this kind of materiales have been paid much attention by scientists at home and abroad.In addition,an in-depth study of their luminescent switching properties is not only important for the regulation of the excited state properties of cycloplatinated（Ⅱ） complexes,but also can greatly expand its application in sensor systems and data security storage.In this thesis,eight luminescent cycloplatinated（Ⅱ） complexes were designed and synthesized by using 2-phenylpyridine as the main ligand andβ-diketone as the auxiliary ligand.Among them,complex 4 has two isomers of yellow-green color（4G）and orange color（4O）.We used UV-Vis absorption spectroscopy,fluorescence spectroscopy,X-ray single crystal diffraction and XRD to systematically study the structure and photophysical properties of the complexes.The results show that the complexes 1,2,4G,5,6 and 7 have mechano-luminescent switching property,while the complexes 3,4O and 8 don’t have mechano-luminescent switching property due to the large substituent steric hindrance.The complex 8 has vapoluminescent switching property that selectively recognizes CH₂Cl₂ vapor.In addition,all complexes have concentration-dependent luminescence switching property in CHCl₃ solution.Through systematic research,we found that the mechano-luminescent switching property of the complexes and vapoluminescent switching property of the complex8 are formed by the formation of an aromaticπ-πstacking interaction between adjacent molecules or the destruction of the F···F interaction during the mechanical grinding process.The concentration-dependent luminescence switching property of the complexes are caused by the aggregation state based on Pt··Pt interaction formed by molecular bending of the complex in high concentration solution.The nature of these luminescent switching properties are the change of the relative energy and the transformation between MLCT and MMLCT of the lowest excited states energy level.