The Construction And Sensing Performance To Small Molecule Amines Of The Eu(?) Tetrahedron Based On ?-diketones

Ln-based sensors have been developed for detecting the species,such as p H,metal ions,anions,reactive oxygen species,amino acids,nitroaromatic explosives and some biomolecules due to their special spectral characteristic,however,the Ln-based complexes are less exploited as sensors for volatile compounds(VCs)detection.Permeability,moderate reactivity,selectivity,reversibility,low detection limit and fast response time are key requirements for the materials to realize the sensing in solid state.In this paper,three series of lanthanide tetrahedral cages were prepared through supramolecular self-assembly,and developed as a luminescence sensor for volatile amines.Firstly,C₃-symmetric tris-?-diketone ligand with the intramolecular charge-transfer(ILCT)characteristic has been designed and synthesized,and its self-assemblies with Ln(?)ions in a 1:1 stoichiometric ratio form the first example of lanthanide tetrahedral cage Eu₄L₄¹ with 3D architecture as a sensor for VCs.X-ray single crystal diffraction analyses confirm the lanthanide tetrahedral cage Eu₄L₄¹ has been synthesised successfully.The Eu₄L₄¹ tetrahedral cage shows highly selective,rapidly reversible,and turn-on emissive responses toward volatile amines/NH₃ in a spin-coated film.Through the comprehensive spectral characteristic and density functional theory calculation,an intermolecular weak nucleophilic interaction is proposed for this response mechanism.Combining this weak interactions with the permeability of the cage,the film presents subsecond to second timescales rapid response;combining the fitting electrophilic capability of the?-diketonate units to amine nitrogen with the tunable intramolecular charge-transfer feature,the cage shows excellent selectivity and turn-on emissive response.This work provides a new clue to develop the lanthanide complexes as luminescence probes for VCs.Secondly,considering the detection of the large bulky biogenic amines,L² with extended triphenylamine scaffold has been designed and synthesized by modifying L¹,and their self-assemblies with Ln(?)ions form Eu₄L₄² tetrahedral cage with larger cavity and rhombus opening.The spin-coated film of Eu₄L₄² presents turn-on emissive,and rapidly reversible responses to some volatile BAs with millisecond response time.For example,the response time of Eu₄L₄² to DAB is estimated to be 87 ms,which is obviously shorter than that of 203 ms for Eu₄L₄¹,which indicating the enlargement of cavity volume of cage increase the porosity of film and reduce response times.Furthermore,vapor phase detection of the BAs was extended to practical application for monitoring fish spoilage.The experimental results affirm the practicability of cage as sensing materials for monitoring food spoilage.In addition,considering the detection of amines in solution,the molecular cage was modified in order to increase the interactions between cages and amines.The ligand L³ has been designed and synthesized by introducing pyridine group into L¹,and its self-assemblies with Ln(?)ions form lanthanide tetrahedral cage Eu₄L₄³.Through the comprehensive spectral characteristics in combination with semiempirical geometry optimization using Lumpac/PM 6 model,it is confirmed that Eu₄L₄³ was prepared.The sensing tests shows the Eu₄L₄³ shows turn-on emissive responses,high selectivity and sensitivity toward volatile amines/NH₃ in THF.This work resolve the response of Eu₄L₄¹ and Eu₄L₄² to amines are not sensitive in solution.For instance,compared with Eu₄L₄¹,Eu₄L₄³ presents the higher sensitivity and lower detection limit for amines.