CPL Study Of Bis-?-diketone Rare Earth Spirochetes Based On Chiral Transfer

Chiral lanthanide supramolecules have been widely used due to their unique circularly polarized luminescence properties in the fields of chiral optical information storage,chiral sensing and chiral optical imaging.However,the synthesis of pure enantiomeric lanthanide helicates was restricted by the limited natural chiral sources and the complicated synthesis routes.Therefore,in this paper,two series of optically pure?-diketone lanthanide helicates were constructed by chiral transfer strategies,and their structures and circularly polarized luminescence properties were studied.The detail works as follows:We designed the bis-?-diketone ligand L with diphenyl sulfide as the spacer.The racemate Ln₂L₃(Phen)₂(Ln=Gd and Eu)were synthesized by reacting the lanthanide ion and the achiral ancillary ligand 1,10-phenanthroline(the molar ratio:L:Ln³⁺:Phen=3:2:2).X-ray single crystal structure analysis exhibited that Eu₂L₃(Phen)₂ was dual-nuclear three-strand helicates.The photophysical test showed that the emission quantum yield of Eu₂L₃(Phen)₂ was 31%.At the same time,supramolecular by chiral phosphine oxide as ancillary ligands(R/S-BINAPO)supramolecular were constructed with the molar ratio of ligand and lanthanide ion(L:Ln³⁺:R/S-BINAPO=3:2:2).Comprehensive spectral characterization and quantitative calculations showed that the introduction of chiral ancillary ligands successfully induced the synthesis of a pair of optically pure dinuclear lanthanide helicates.Based on the good sensitization ability of?-diketone units and the chiral amplification of helicates,the physical test showed that the emission quantum yield of Eu₂L₃(R/S-BINAPO)₂ was 34%,and |g_lum|reached 0.112.We designed the double?-diketone ligand L' with biphenyl derivative as spacer,which self-assembled with Ln³⁺ion at a molar ratio of 2:1 to form a binuclear quadruple-stranded racemate(HEt₃N)₂Ln₂L?₄.Induce and separate chiral helical products were obtained by replacing the achiral counterion HNEt³⁺with a chiral counterion guanidine salt 1,3-bis(R/S)-1-phenylethylguanidine hydrobromide R/S-BPG.The comprehensive spectrum exhibited that a pair of enantiomerically pure lanthanide complexes was successful constructed.In addition,circular dichroism and circularly polarized luminescence spectra further demonstrated the existence of stable ground state and excited state in solution.The photophysical test exhibited that the luminescence quantum yield of(R/S-BPG)₂Eu₂L'₄ was 51%,and |g_lum| reached 0.105.The above results indicated that chiral ancillary ligands and counterion induction strategies can easily be synthesized materials with good CPL performance.