Synthesis And Properties Of Chiral Rare-Earth Europium Complexes

Rare-earth resources in China are rich with various kinds and abundant reserves.The research on rare-earth coordination compounds has been one of the frontier fields in the research of rare-earth chemistry.Compared with transition metal elements,rare-earth elements have more unique electronic structures,and complexes formed by rare-earth elements also have unique optical,electrical and magnetic properties.Chirality,as a sign of nature,exists widely in nature and life.It has always occupied an important position in the field of science and technology,and it is an important subject in molecular research.Therefore,the introduction of chirality into rare-earth complexes is very attractive.Chiral rare-earth complexes have attracted many people to study because of their unique topological structure,and excellent properties in the fields of electronics,magnetism,photochemistry and catalysis.In this paper,the chiral ligand R/S-(-)(+)-1,1'-Binaphthyl-2,2'-diyl hydrogenphosphate and Eu(NO₃)₃·5H₂O salt were used as raw materials to design and synthesize three opponents.The complexes of rare-earth europium,and their structures and properties have been systematically studied.The study of chiral fluorescence sensing to identify enantiomers has attracted many attention because of their time-saving,high sensitivity and low cost.Therefore,in recent years,many researches focused on the development of enantiomeric fluorescence sensors for chiral recognition.Chiral recognition has also been studied by scientists.Previously,chiral recognition mainly focuses on the recognition of amino acids,but there are relatively few studies on the recognition of binaphthyl and its analogues,and the complex structure as a fluorescent sensor is complicated and difficult to synthesize.Chiral rare-earth complexes have attracted wide study because of high coordination number(the coordination number is generally 6 to 12),their good luminescence properties,and characteristic geometry.In this thesis,a chiral europium complex was synthesized in one step by a water/solvothermal method.The complexes have both optical activity and chirality,and can effectively identify binaphthol and its derivatives.The research content of this paper includes the following two parts:1.We designed and synthesized a pair of di-nuclear europium enantiomers[Eu₂(PO₄)₆(R/S-HL)₆(Me OH)₄]·2Me OH(R/S-Eu(2))uses chiral ligands R/S-(-)(+)-1,1'-Binaphthyl-2,2'-diyl hydrogenphosphate(R/S-HL)and hydrated salts of Europium(III)nitrate as raw materials under water/solvothermal method.We described the crystal structure in detail.The structure of the crystal(R/S-Eu(2))was tested with a single crystal X-ray diffractometer,and it was found that the crystal,located in the chiral space group P4₃2₁2,was a zero-dimensional cluster structure,with two Eu(III)ions located in the center of the structure and are encompassed by seven oxygen atoms to form the model of distorted octahedron.The study of circular dichroism shows that the complex R/S-Eu(2)is a good pair of chiral enantiomers,which is consistent with the results of single crystal analysis.In addition,we also performed other characterization and analysis of the complex R/S-Eu(2),including XRD,infrared and ultraviolet.Importantly,we have found the fluorescence sensing properties of the di-nuclear Eu(III)complex and proved that the complex R-Eu(2)has a good enantiomer to(S)-BINOL(ef=0.78)and its derivatives selective.And in the range of 1×10^-7 mol/L to 1×10^-4mol/L,the sensor(R-Eu(2))has higher sensitivity for the determination of ultra-trace S-BINOL.2.We used the R/S-Eu(2)crystals synthesized in the first part as raw materials by adding the second-ligand oxalic acid and methanol solvent to synthesize[Eu₄(COO)₂(PO₄)₈(R/S-HL)₈(Me OH)₂]·6H₂O(R/S-Eu(4A))complex.Then,we designed and synthesized another pair of tetra-nuclear europium enantiomers[Eu₄(PO₄)₉(R/S-HL)₈(NO₃)(OH)₃](R/S-Eu(4B))uses R/S-(-)(+)-1,1'-binaphthyl-2,2'-dihydrophosphate(R/S-HL)as the chiral source and Europium(III)ion as the metal center.Both of these complexes are chiral complexes.We described the crystal structure in detail.The results of single crystal diffraction show that the complexes are all chiral complexes.R/S-Eu(4A)belongs to the chiral P1 space group and crystallizes in the orthorhombic system,while R/S-Eu(4B)is located in the chiral C2 space group and crystallizes in the monoclinic system.The complexes are all zero-dimensional metal clusters.Structural analysis shows that both complexes have four europium ions as the metal center.In the(R/S-Eu(4A))complex,the central molecular entity contains one[(COO-)₂]^2-,four Eu(III)ions,eight S-HL ligands and eight-OH.The complex S-Eu(4A)has a[(COO-)₂]^2-nucleus,four metal atoms on a plane,arranged in a known twisted butterfly conformation.In the complex(R/S-Eu(4B)),the central molecular entity contains one PO₄^2-ion,four Eu(III)ions,eight S-HL ligands and four-OH.The complex S-Eu(4B)has a PO₄^2-core,four metal atoms on a plane,arranged in a twisted diamond lattice configuration,and a coordination between P and Eu is also formed.Both pairs of enantiomeric complexes have been characterized and analyzed.At the same time,X-ray powder diffraction,infrared spectroscopy,ultraviolet spectroscopy,circular dichroism,etc.were used for testing,and all spectra were analyzed.Circular dichroism analysis shows that the chirality of the complexes comes from chiral ligands.