Fluorescence Studies of Curcuminoids And Their Lanthanide Complexes

Abstract

The fluorescence studies of eight curcuminoid analogues (HL1 to HL8 ) were carried out to correlate the effect of aryl substituents and conjugation on fluorescence emission maxima. The results revealed that in curcuminoids containing unsubstituted aryl rings (HL1 , HL2 and HL3 ), fluorescence maxima increased as the degree of conjugation increases. Electron donating substituents in the para position of the phenyl rings showed highest fluorescence emission maxima. The fluorescence emission spectra of the Ln(III) complexes of HL7 (curcumin I) are broad and their λmax of fluorescence are very close to that of the ligand except for the Eu(III) complex. This indicates that no appreciable change in the energy levels of the ligand has occurred during complexation