Synthesis Of Rare Earth Complexes With Hydroxamic Acid And Study On Its Fluorescence Sensing Properties

Lanthanide ions have been endowed with the unique photophysics properties due to the specific 4f electronic configurations.When lanthanide ions form stable complexes with organic ligands with high conjugation,absorption coefficient and transfer efficiency,they can exhibit excellent luminescence properties,thus the luminescence emission intensity and decay of lanthanide ions can be exceedingly enhanced.In this paper,two series of lanthanide complexes with different structures have been designed and synthesized by salicylhydroxamic andβ-diketonate dibenzoylmethanide adopting solvent diffusion method.Afterwards the structures of these complexes were determined by single crystal X-ray crystallographic studies,furthermore,the luminescence properties and applications were investigated.The results are listed as following:1.A series of dinuclear Ln-complexes[Ln₂（Hshi）₂Cl₄（NO₃）₂·2MeOH]·Et₃N[Ln=Sm（1）,Eu（2）,Tb（3）,Dy（4）]were synthesized by reactions between salicylhydroxamic and mixed lanthanide,LnCl₃ and Ln（NO₃）₃ under the same reaction conditions.The emission of complexes 1 and 3 exhibits dual luminescence from ligand and corresponding lanthanide ions;The luminescence of complex 2 demonstrates characteristic luminescence of Eu³⁺ions;Complex 4 shows dual luminescence emission dominated by ligand and supplemented by Dy³⁺ions.2.A series of dinuclear lanthanide complexes[Ln₂（Hshi）₂DBM₄·2DMF][Ln=Sm（5）,Eu（6）,Gd（7）,Dy（8）,Nd（9）,Yb（10）]were synthesized by reactions between salicylhydroxamic and the precursor Ln（DBM）₃ under the same reaction conditions.The optical luminescence properties,including intensity,decay lifetime and quantum efficiency,have been outstandingly enhanced by doping method.The luminescence of complexes 5 and 6 demonstrate characteristic luminescence of corresponding Ln³⁺ions in the visible region;Complexes 9 and 10 exhibit typical NIR-emitting lanthanide³⁺ions.New single component white-light emitting materials were developed by adjusting appropriate excitation wavelength to radiate complex 5.Similarly,complex 8 shows the luminescence of ligand-self.Taking advantage of this character,another white-light emitting materials were obtained by the combination Eu³⁺and Dy³⁺from corresponding Ln-compounds with a two-component approach.Through the phosphorescence test of complex 7,the relationship between luminescence intensity and lifetime of complex and energy level difference between the ligand and lanthanide ions was described in detail.3.Doped materials Eu_0.2Gd_0.8 can emit strong red light in the visible region to realize selective sensing of acetic acid small molecules,aluminum ions and dichromate.Quantitative analysis proved that the doped materials were highly sensitive to the above guest molecules.Acetic acid small molecules and dichromate cause quenching effect on doped materials and aluminum ions change their luminescence color from red to blue-green.This work is expected to provide a new reference for the fluorescence detection applications of lanthanide complexes.