Synthesis And Luminescence Performance Of Neodymium Complexes With A Aggregation Induced Near-infraed Emission Based On Tetraphenylethylene Derivatives

Aggregation-induced phosphorescence enhancement（AIPE）-active materials are promising in various applications such as luminescence sensing,optical de vices and so on.Owing to the bright emission,superior photostability,and biocompatibility,it is believable that the AIPE-active probes are promising in long-term and in-depth imaging and tracing applications.Due to the electron transitions of outer shell of metallic subunits and AIE-active ligands,their excitation energies are susceptible to external stimuli.Therefore,it is not simply to combine metals and AIE-active ligands for AIPE-active metallic compounds,their variable excitation energies depending on peripheral environments should be matched each other.For the above reason,till now few examples of AIPE activity based on discrete coordination complexes compared with the AIE-active organics.Although the reported AIPE-active transition metal complexes include Re^I,Ir^III,Pt^II,Au^I,Zn^II,Cu^Iand Pd^II,AIPE luminosity in bio-imaging,which needs large Stokes shift and long luminescence lifetime to eliminate autofluorescence from biological sample through time-gated technique,is still very limited,it is therefore necessary to develop new AIPE-active materials for bio-probes in living cells.By studying the photophysical properties and revealing the mechanism of AIPE behaviors,we conclude some new insights and provide some suggestions on designing a new AIPE system.Anchoring AIE-active organic linkers to metal ions within a robust matrix of MOFs,their turn-on emission mainly originates from the twisted linker conformation,intramolecular hindrance,as well as the framework rigidity caused by the restricting intramolecular motions（RIM）of linkers,which diminish the non-radiative energy loss.Taking advantages of the electronic properties of metallic subunits with triplet excited states,it is possible to construct diverse AIPE-active metal complexes by incorporating a rotating or isomerizable unit in the ligand,structural rigidification effects or isomerization activate the RIR process inducing highly phosphorescent in aggregation.Owing to the forbidden Laporte rule and low molar absorption coefficient,the lanthanide ions could only be efficiently populated by adjacent absorbing light harvesting,which act as the sensitizers to pump their excited energies into the one of lanthanide by antenna effect.By reason that the shielding effect induces the internal f-f‘electron transition of lanthanide ions,we may realize AIPE-active lanthanide complexes through ³LMCT and antenna effect.Since the elongated lifetimes of highly efficient luminescence of lanthanide span visible to NIR region,it is suitable for developing new AIPE-active bio-probes.However,to the best of our knowledge,AIPE-activity of lanthanide compounds has yet to be reported till now.Due to of the special photophysical properties of lanthanide complexes,they has been widely researched and applicated in the fields of OLED devices,chemosensors,cell imaging and so on.But they often sufferd the notorious ACQ effect,which hampers their practical applications.Very Recently,a luminescent lanthanide complexes[TPE-TPY-Eu（hfac）₃]（hfac^-=hexafluoroacetylacetonate;TPE-TPY=4’-（4-（1,2,2-triphe-nylvinyl）phenyl）-2,2’:6’,2’’-ter pyridine）was reported in our group.In which,the planar hfac^-exhibits bright emission in dilute solution,whereas the other―bladed‖structural TPE-TPY shows AIE-activity at high concentrations.These two types of sensitizers stepwise light up the lanthanide emission by modulating the concentrations.Herein,we prepared a series of AIPE active[L₂-Nd（NO₃）₃],where L refers to 2,2’-bipyridine derivatives including TPE-BPY（L1）and TPE₂-BPY（L2）,respectively and discussed their structure-property relationship.The first chapter is the preface,it briefly described the research progress and development of AIPE-active metallic complexes,and discussed the novelty,bottleneck and possible solutions base on the AIE-active TPE of NIR lanthanide complexes.The second chaper:Two ligands TPE-BPY（L1）and TPE₂-BPY（L2）were synthesized by Suzuki-coupling reaction,their AIE-activities are also discussed and confirmed.Multiple inter and intramolecular C-H···πinteractions should be responsible for their AIE behaviors.In the solid state,L2 shows a blue-green emission at 500 nm with a quantum yield of 23.7%and a lifetime（τ）of 1.85 ns,while L1 exhibits a deep blue emission at 470 nm with a higher quantum yield of 73%and a longer lifetime（τ）of 2.38 ns.The high quantum yield and high blue color purity enable L1 acting as promissing emisive layer in blue OLEDs.Chaper 3:We successfully prepared two―bladed‖structural[（L）₂-Ln（NO₃）₃]（Ln=Nd;L=L1,L2）by chelating Nd^III ion with AIE-active TPE derivatives,and utilized UV-vis and luminescence including variable concentration to unveil the ³LMCT from BPY derivatives to Nd^Ⅲprocess.The calculated triplet-state energy level(16900～17150cm^-1)of[（L）₂-Ln（NO₃）₃]（Ln=Gd;L=L1,L2）proved that both of these ligands are favorable for energy transfer into Nd³⁺.It is the first example of lanthanide complexes to show AIPE performance by structural rigidification to decrease the dissipation of excited energies,thus broadening the AIPE family from transition metals to lanthanides,stepwise improving Nd^III phosphorescent emissions by quantity of AIE-active sensitizers.Such approaches could improve theΦof NIR phosphorescent emission of Nd^III of[（L₂）₂-Nd（NO₃）₃]up to 4.5%in solid state.Also,the AIPE-active lanthanide complexes is promising in OLED application.