A New Ligand for Europium(III) That Forms a Stable Fluorescent Complex in Aqueous Solution

A new macrocyclic ligand for Eu3+, 24, 30-diphenyl-8, 19-(1, 21 : 4, 6 : 10, 12 : 15, 17-tetraetheno-8, 9, 19, 20-tetrahydro-7H, 18H-dibenzo[b, k][1, 4, 7, 10, 13, 16]hexaazacyclooctadecine)diacetic acid (1), was synthesized and its fluorescence characteristics were examined, particulary to compare with 4, 7-bis(chlorosulfophenyl)-1, 10-phenanthroline-2, 9-dicarboxylic acid (BCPDA) that has proved to be useful as a label in time-resolved fluoroimmunoassays. The complex of macrocycle 1 with Eu3+ was found to have a higher fluorescence intensity as well as a longer fluorescence lifetime than that of BCPDA.