Luminescent Macrocyclic Lanthanide Complexes Bearing N-Oxides: Potential Fluorescent Labels for Modern Medical Diagnostics

Macrocyclic and macropolycyclic ligands incorporating heteroaromatic N-oxides (3,3'-biisoquinoline-2,2'-dioxide) form strongly luminescent complexes with lanthanide ions: Eu(III) and Tb(III). Most of these complexes are stable water solutions, with excellent luminescent properties, regarding luminescence lifetimes in the range of 0.2-0.7 ms, and the quantum yields for emission up to 0.25. Several complexes are stable also in the presence of affecting ions, such as Ca(II), or phosphates. These features make them attractive as potential fluorescent labels for time-resolved fluoroimmunoassays.