Structure Control Of Rare-Earth Supramolecular Complexes Based On Tetradentate Hydrazone Ligands

Supramolecular chemistry is a discipline that investigates the weak intermolecualr interactions.It encompasses many fields,such as chemistry,biology,materials,physics,etc.Thereinto,coordination-directed self-assembly is an effective means to construct supramolecular organic complexes with exquisite architectures and specific sizes from simple building blocks under the drive of coordination.Introducing rare earth ions into the complexes as metal centers can not only construct supramolecular complexes with complicated structures,but also endow them an abundant of optical,electrical and magnetic properties.Traditional multi-nuclear rare earth complexes are mostly cationic complexes constructed from three tridentate ligands in a nine-coordination mode.The poor-stability,and the coordinated saturation rare earth ion centers make subsequent functional applications great restriction.In this thesis,a series of tetradentate acylhydrazone ligands were designed and synthesized based on the synthesis strategy of coordination-directed self-assembly,and their base-and metal-dependent self-sssembly was studied.Moreover,their luminescence properties in the near-infrared were explored.The specific research works are as follows:1.In chapter 1,we introduced the research background of this thesis from the excellent optical properties of rare earth elements.Several types of classical rare earth organic supramolecular complexes were shown.Based on the overview of the current research process and challenges,the purpose and significance of this thesis are proposed.2.In chapter 2,we designed and synthesized meta-bitetradentate acylhydrazone ligand H4L1 and para-bitetradentate acylhydrazone ligand H4L2,and discussed their assembly behaviors under different conditions by NMR,ESI-TOF-MS and SC-XRD.In the absence of base,H4L1 assembles into a dinuclear double-stranded helical complex Ln2(H2L1)2 by spontaneously partially deprotonating with light rare earths and middle rare earths such as La3+,Sm3+or Eu3+.When the metal is replaced with heavy rare earths,such as Yb3+and Lu3+,trinuclear cyclic Ln3(H2L1)3 were formed.For H4L2,under neutral conditions,partial deprotonation assembly can produce infinite one-dimensional metal-organic polymer chains(Ln2H2L2)n.In the presence of base,completely deprotonated[L1]4-and[L2]4-are assembled with lanthanide metals to form discrete tri-nuclear Ln3(L1/2)3 and quaternary Ln4(L1/2)4 macrocyclic structures.For these macrocycles,there are multiple isomers coexisted in the solution.We enumerated the possible isomers and simulated these possible isomers using molecular mechanics models.All Yb complexes exhibited good visible light-sensitized near-infrared emission.3.In chapter 3,a tritoptic tetradentate acylhydrazone ligand H6L3 with C3 symmetry was designed and synthesized,and its self-assembly behaviors with rare earth ions were studied by NMR,ESI-TOF-MS and SC-XRD.Under neutral conditions,H6L3 assembles into six-nuclear tetra-capped octahedral Ln6(H3L3)4(OTf)6 with middle and heavy rare earths such as EuⅢ,YbⅢ and LuⅢ.However,tri-nuclear Ce3(H3L3)2(OTf)3 and La3(H3L3)2(OTf)3 and tetra-nuclear La4(H3L3)2(OTf)6 were obtained from light rare earth ions LaⅢ and CeⅢ.Under basic conditions,all rare earth ions formed six-nuclear tetra-capped octahedral(Et4N)6Ln6(L3)4.There are multiple isomers coexisted in the solution.Homochiral isomers were prepared by two methods.We have captured the crystal structure of The kinetic mesomeric isomers ΔΔΔΛΛΛ-(Et4N)6Eu6(L3)4 and thermodynamic homochiral isomers ΔΔΔΔΔΔ/ΛΛΛΛΛΛ-(Et4N)6Ce6(L3)4.Both Yb6(H3L3)4(OTf)6 and(Et4N)6Yb6(L3)4 exhibit good visible light-sensitized near-infrared emission.Moreover,ΔΔΔΔΔΔ/ΛΛΛΛΛΛ-K6Lu6(L3)4 could encapsulate cationic tetra-alkyl ammonium by host-guest interaction.This thesis revealed the diversity of rare earth supramolecular assembly structures,and provides new choice for the design of optical functional materials.