Lanthanide Ion Intraction with a Crown Ehtr Methacrylic Polymer,Poly(1,4,7,10-tetraoxacyclododecan-2-ylmethyl methacrylate),as Seen by Spectroscopic,Calorimetric,and Theoretical Studies

摘要

The interacton between trivalent lanthanide ions and the polymer poly(1,4,7,10-tetraoxa-cyclododecan-2-ylmethyl mthacrylate)(PCR4) containing pendant 1,4,7,10-tetraoxacyclododecane (12-crown-4)groups has been studied by various spectroscopic techniques,calorimetry and theoretical calculations.Evidence for the binding of Eu(III),Tb(III),and Ce(III) ions and PCR4 in solution was obtained by the lanthanide-induced ~1H and ~13C NMR shifts and the decay of Tb(III) bound to PCR4 in H_2O and D_2O solutions,it is suggestedthat ocmplexation leads to a decrease in the number of water molecules from 8 or 9 to 7.In the solid state,studies bydifferential scanning calorimetry (DSC) show that the interaction between Ce(III),Tb(III),and Li(I) ions and PCR4 leads to an increase in the glass transition temprature (T_g) of the polymr.Electron paramagnetic resonance(EPR) spectra of Gd(III) in eh presence of the polyme rare quite similar to those in aqueous solution,while Tb(III) emission is quenched by Ce(III) with nearly the same rated constants in water and aqueous PCR4 solutions,and the Ce(III) emissionmaxima are only very slightly shifted in the presence of the polymer,all suggesting relatively weak dynamic interaction between the cations and the crown ether.However,isotope effects on the Tb(III) luminescencelifetime confirm complexation.From the lanthanide-induced ~1H and ~13C NMR shifts the stability constnats of the 1:1 complexesformed havebeen calcualted for both Tb(III) and Eu(III),yielding values 22.5 and 1.9,respectively.The agreement between the constants confirm the weak bidning of the lanthanide ions by the crown ehter.Results of ab initio calculations are also reported,where the interactions are modeled for 12-crown-4/La(III) compelx and bond energies determined.