Design And Application Of Polynuclear Lanthanide Complexes

Many rare earth complexes have characteristic emission spectra?narrow peaks,large Stokes shift,long luminescence lifetime?and various coordination models.It has become one of the most important research aspects in coordination chemistry to understand the novel structure of rare earth complexes and exploit their valuable function.This thesis is focusing on the structural design and functional application of different polynuclear lanthanide complexes with unique structural type,multi-metal centre,size or chirality,which are self-assembled and constructed respectively by a series of multidentate ligands,including multidentate Schiff base ligands,multidentate chiral dihydrazone ligands,and multidentate achiral dihydrazone ligands.Moreover,the regulation of these polynuclear lanthanide complexes in controlling structural change,tuning near-infrared emissions,achieving selective response in luminescence,introducing chiral recongnition,and improving chiral catalysis are researched and discussed in detail.This paper will be divided ito six chapters:Chapter 1:This section briefly introduced the background of supramolecular chemistry and lanthanide coordinated chemistry.And then,the researth progress on the synthesis of chiral lanthanide complexes and the application in recognition,sensing,asymmetric catalysis as well as the luminescent selectivily response of achiral lanthanide complexes was reviewed.Chapter 2:We designed and synthesized a kind of semi-rigid pentadentate ligand,which could capture effectively Yb³⁺ion to form stable Yb³⁺near-infrared luminescent complex and further provide potential cavity to accommodate alkali metal ions.A series of novel s-f heteronuclear complexes suggested that the compositional differences of these complexes mainly originated from the different radii of alkali metal ions.Notably,only K⁺-induced Yb³⁺complex presents distinctive1D coordination polymer chain with rapid growth due to suitable ion radius.The process based on K⁺-induced self-assembly was utilized to obtain stable crystalline Yb³⁺complex-based NIR membrane material through in situ induced growth strategy under mild conditions.Chapter 3:We designed and synthesized a series of unique homochiral lanthanide tetranuclear quadruple-stranded helicates,which were self-assembled controllably by taking the intrinsic advantages of chiral and semi-rigid bridging ligands and lanthanide ions with high coordination numbers.The self-assembly process of these chiral helicates not only ensures the structural stability and quadruple-stranded feature of lanthanide cluster in solid and solution,but also achieves the effective transfer and amplification of chirality code from ligand to higher supramolecular level.Moreover,through using optical rotation,circular dichroism spectra analysis and luminescence measurement,these chiral lanthanide helicates could serve as sensitive and multi-responsive sensors to recognize and detect F^?anions based on the change of chiral signal and NIR luminescence simultaneously.Chapter 4:We designed and synthesized another a pair of enantiomerically pure chiral dihydrazone ligands with different rigid and extension direction based on chiral tartaric acid.The unique homochiral hexanuclear sextuple stranded cyclic Nd³⁺complex and homochiral decanuclear octuple stranded cyclic Er³⁺complex have been obtained successfully.Further,we measured CD spectrum and near-infrared emission of these chiral polynuclear lanthanide complexes,which showed effective transfer of chirality from ligand to higher supramolecular level and better antenna effect.Chapter 5:We designed and synthesized flexible dihydrazone ligand,which could coordinate with lanthanide ions to form another type of tetranuclear quadruple-stranded helicates and assemble with lanthanide ions and transtition metal ions(Zn²⁺)to form novel fourteen nuclear 3d-4f heterometal complexes.The structures and self-assembly of these polynuclear lanthanide complexes were studied,and their catalytic abilities for cycladdition reaction of epoxides in the presence of CO₂ were exploited due to multi-metal active centers in the complex.The feasible catalytic mechanism of polynuclear lanthanide complexes was analyzed and showed.Chapter 6:We designed and synthesized another flexible dihydrazone ligand with different terminal group based on the chapter 5,which could coordinate with lanthanide ions and mixed metal ions?lanthanide ion and transtition metal ions?to form dinuclear double helix complex,tetranuclear double helix complex and octanuclear quadruple-stranded helicates,respectively.The regulation factor of different structures were studied and the catalytic abilities of these polynuclear lanthanide complexes for cycladdition reaction of epoxides in the presence of CO₂ were researched.