Synthesis,Characterization and Fluorescence Property of Dy~(3+) with Halobenzoic Acid and Nitrogen-heterocyclic Complexes

Five complexes of dysprosium were synthesized,in which benzoic acid or halobenzoic acids were as the first ligand,and nitrogen-heterocyclic(phenanthroline or 2,2'-dipyridine) as the second ligand.By elemental analysis,rare earth coordination titration,the compositions of the complexes were confirmed to be Dy(BA)3(bpy),Dy(BA)3(phen),Dy(ClBA)3(phen)(EtOH),Dy(BrBA)3(phen)(EtOH) and Dy(IBA)3(phen)(EtOH),(BA=benzoic acid,ClBA=p-Cl-benzoic acid,BrBA=p-Br-benzoic acid,IBA=p-I-benzoic acid,bpy=2,2'-dipyridine,phen=1,10-phenanthroline),respectively.The ligands and coordination compounds were studied by means of IR spectra,UV-spectra,fluorescence excitation and emission spectra.The results showed that benzoic acid or halobenzoic acid is bonded with Dy(Ⅲ) through oxygen atoms in the carboxyl group,and phen or bpy ligands is bonded to Dy(Ⅲ) through nitrogen atoms.Fluore-scence emission spectra indicated that the fluorescence emission intensity of Dy(ClBA)3(phen)(EtOH) is the strongest,Dy(BrBA)3(phen)(EtOH) is second,and Dy(IBA)3(phen)(EtOH) is the weakest among the Dy(Ⅲ) with halobenzoic acid and phen complexes.The intensity of Dy(BA)3(bpy) is little stronger than Dy(BA)3(phen) at about 481 nm,but at about 573 nm,Dy(BA)3(phen) is more stronger.The 4F9/2 energy of Dy3+ ion is 20 509 cm-1,the triplet energy of phen is higher than the excitation energy of Dy3+ ion,thus the absorbing energy of phen can effectively transferred to Dy3+ ion,and producing a characteristic spectrum.The fluorescence intensity of Dy(ClBA)3(phen)(EtOH) is the strongest among the three halobenzoic acid complexes,it shows that the triplet state energy of p-Cl-benzoic acid matches well with the lowest excitation energy of Dy3+ ion.