Synthesis,Thermodynamics and Fluorescence Properties of Ether-Functionalized Based Rare Earth Ionic Liquids

Author:Zheng Ling

Supervisor:fang da wei


Degree Year:2018





In this paper,four novel ether-based rare earth ionic liquids[MOEMIm][Ln(NO3)4](Ln=Sm,Eu,Tb,Dy)with special fluorescent properties were synthesized by using1-methoxyethyl-3-methyl-imidazole as a cation and nitrates of lanthanide-containing Sm,Eu,Tb and Dy as anions.The structures of ionic liquids were characterized by 1H NMR,13C NMR and anion-cation electrospray ionization mass spectrometry.The density,surface tension,conductivity and refractive index of ionic liquids[MOEMIm][Ln(NO3)4](Ln=Sm,Eu,Tb,Dy)were measured in a certain temperature range by using standard addition method.The relationship between experimental results and temperatures was discussed by linear regression equation with the properties values without water of ionic liquids.The results show that the four ionic liquids have similar properties and their density,surface tension and refractive index decrease with increasing temperature,and the conductivity increases significantly with increasing temperature.According to the Glasser theory using the densities of ionic liquids[MOEMIm][Ln(NO3)4](Ln=Sm,Eu,Tb,Dy),the volumetric properties,standard entropy and lattice energy(298.15 K)were estimated and discussed.The surface energy and surface entropy were investigated according to surface tension.The results showed that the surface energies were similar and the surface entropy slightly decreased with the increase of temperature.The speed of sound of ionic liquids was discussed by using the density and surface tension properties,and the speed of sound decreased with the increase of temperature.The molar polarization and polarizability are discussed in terms of density and refractive index values,both of which almost unchange with changes in temperature.In addition,Arrhenius equation and Vogel-Fulcher-Tammann(VFT)equation were used to discuss the conductivity of the four ionic liquids,respectively.The results show that the VFT equation is more suitable for discussing the relationship for ionic liquids[MOEMIm][Ln(NO3)4](Ln=Sm,Eu,Tb,Dy)between the conductivity and temperature.The constant pressure molar heat capacities(molar heat capacity)of four hydrophilic ionic liquids[MOEMIm][Eu(NO3)4],[C5mim][Lact],[C4mim][Ser],[C2py][DCA]and hydrophobic ionic liquid[C2py][NTf2]were determined.The polynomial fitting results show that the molar heat capacities of the four hydrophilic ionic liquids gradually increase with increasing temperature in a certain temperature range and hydrophobic ionic liquid[C2py][NTf2]has a phase transition within the test temperature range.The melting point of[C2py][NTf2]was obtained through the discussion of the experimental data of the phase transition process.The influence of the trace impurities in the ionic liquid on the melting point was discussed by using the freezing point descending method from the phase equilibrium theory.The results show that the freezing point descending method is suitable for discussing the melting point(freezing point)of ionic liquid and calculating the molar enthalpy of fusion and the molar melting entropy of[C2py][NTf2].The molar enthalpy of five ionic liquids at 298.15 K was obtained by the polynomial fitting equation.The molar heat capacity of five ionic liquids was estimated by using the molar volume,temperature,atomic number and molar mass of the ionic liquids.In addition,the constant volume heat capacities of five ionic liquids were calculated based on the experimental results and literature values of density,speed of sound and molar heat capacity.The ionic liquids[MOEMIm][Ln(NO3)4](Ln=Sm,Eu,Tb,Dy)exhibited good fluorescent property,which all had different strong fluorescence color under UV-light irradiation(λ=365 nm).As fluorescence-quenching sensors,the trace amounts of quenchers o-(m-,p-)nitrotoluene make the fluorescence intensity decrease and produce significant fluorescence quenching.Additionally,p-nitrotoluene gave the most significant fluorescence quenching effect among the three isomeric nitrotoluenes.What’s more,the two fluorescent ionic liquids demonstrated high selectivity toward nitrotoluene even in the presence of methylbenzene,phenol,chlorobenzene,aminobenzene.Hence,the ionic liquids have selectively recognition of nitrotoluene from aromatic compounds.