Syntheses,Structures And Luminescent Properties Of Lanthanide Clusters With ?-dinetonate Ligands

Lanthanide have excellent optical properties such as narrow emission spectra,large Stokes shift,millisecond luminescence lifetime and wide luminescence region that crossing the visible to near infrared,attractting extensive attention in the research such as bioprobe,luminescent chemical sensorsoptical,lasers and luminescence thermometer.The lanthanide clusters have nanoscale molecular structures and exhibit abundant physical and chemical properties.However,the coordination of solvent molecules and hydroxyl bridge vibration quench the luminescence of lanthanide and limit the research of luminescence properties of the lanthanide clusters.Reducing energy loss of non-radiative transition process in the luminescence process and improving quantum yield of the lanthanide clusters is remain a challenge in the research of the lanthanide cluster luminescent materials.?-diketonate ligands with high absorption coefficient has been successfully applied to the construction of mononuclear lanthanide complexes luminescent materials.The fluorinated ?-diketonate ligands can reduce energy loss and improve luminescence efficiency.Therefore,acetylacetone and trifluoroacetylacetone ligand were selected to synthesize lanthanide clusters,and the synthesis conditions,structural characteristics,and luminescence properties of lanthanide clusters were investigated in this thesis.The specific contents are as follows:1.The luminescence properties of a nine-core rare earth cluster Ln9 with acetylacetone as the ligand was selected to study.The dual-emitting clusters was obtained by Eu/Tb doping and the temperature dependent luminescence intensity of Ln9 were investigated.The results show that the luminescence intensity of Ln9 can sense the change of temperature.Ln9 has the potential as a luminescence thermometer.2.Two dodecanuclar lanthanide clusters Tb12 and Dy12 with trifluoroacetylacetone ligand were obtained at low temperature.The luminescence properties of Tbi2 were investigated at room temperature and it is found that Tbi2 in solid exhibits intense green luminescence with a quantum yield of 21.2%and a lifetime of 306 ?s.A small amount of Eu was doped in Tbi2 can regulate the luminescent color from green to orange red,and the Eu/Tb dual-emitting cluster Ln12 was used for the study of temperature dependent luminescent properties.The luminescence intensity of the doped sample Eu0.5Tb11.5 changed significantly with temperature and the sensitivity of the 270 K-300 K temperature range is 3.36%/K,which turn out that Ln12 can be a good material as molecular luminescent thermometer.3.Three isomorphic hexadecanuclear lanthanide clusters Eu16,Sm16and Gd16 with trifluoroacetylacetone ligand were obtained at low temperature.The luminescence properties of Eu16 and Smi6 were tested resulting that Eu16 exhibits intense red luminescence both in solid state and in the solution with acetonitrile,the quantum yield are 12.8%and 5.7%,respectively,and the lifetimes are 361 ?s and 803 ?s,respectively.The growth mechanism of Eu16 were investigated by high-resolution electrospray ions mass spectrometry.The cluster Eu16 gradually nucleated during the addition of triethylamine,forming the tetranuclear cluster first,then the intermediate Eu8,Eu9,Eu10 and Eun,forming Eu16 finally.