Synthesis And Properties Of Cyclometalated Pt(Ⅱ) Complexes With 2,2’-Bipyridine Ligand

Cyclometalated platinum(Ⅱ)complexes have rich luminescence properties and unique planar quadrilateral structure,which makes them have important research value in the fields of aggregation-induced emission(AIE)and self-assembly.At present,most of the reported AIE materials are small organic molecules.There are relatively few reports on the AIE properties and self-assembly properties of cationic cyclometalated platinum(Ⅱ)complexes based on 2,2’-bipyridine ligands.According to the AIE mechanism of restriction of intramolecular rotations(RIR)and restriction of intramolecular vibrations(RIV),AIE-active cyclometalated platinum(Ⅱ)complexes might be designed and synthesized by adjusting the structures of cyclometalating ligands.At the same time,the unique planar structure of platinum(Ⅱ)complex will lead to the unsaturated axial coordination of the complex,resulting in the formation of intermolecular interaction and self-assembly.More importantly,the rich luminescence properties of cyclometalated platinum(Ⅱ)complexes make them visible in the process of self-assembly,which greatly facilitates the study of self-assembly properties.Thus,the main research content of this paper includes the following two parts:1.Design and synthesize four cationic cyclometalated platinum(Ⅱ)complexes Pt1-Pt4 with 2,2’-bipyridine as auxiliary ligand,2-phenylpyridine and its phenyl-modified derivatives as cyclometalating ligand.The photophysical properties and luminescent properties in acetonitrile-water of cyclometalated platinum(Ⅱ)complexes were systematically investigated.It is found that the complexes Pt1-Pt4 exhibit obvious AIE properties.Among them the complex Pt3 with a phenyl moiety at the meta position of the benzene ring of 2-phenylpyridine demonstrates the best AIE properties.2.Based on the photophysical properties of complex Pt3,five cationic cyclometalated platinum(Ⅱ)complexes Pt5-Pt9 were designed and synthesized with 2,2’-bipyridine as auxiliary ligand and fluorinated 2-(3-biphenyl)pyridine derivatives as cyclometalating ligand.The effects of the substitution positions of fluorine atom on the AIE properties and selfassembly properties of cyclometalated platinum(Ⅱ)complexes were systematically investigated.It is found that the complexes Pt5-Pt9 are AIE-active.The time-dependent UVVis absorption spectra show that Pt5 forms two different aggregates in acetonitrile-water system.The formation of these two aggregates belongs to a competitive pathway,and the assembly mechanism of agg Ⅱ follows the nucleation-elongation model.