Twelve heteroaromatic complexingagents 9a–I were synthesized with the purpose to develop suitable labels for time-resolved luminescence-based bioaffinity assays. The relative luminescence yields, excitation maxima, and emission decay constants of their europium(III) and terbium(III) chelates were determined. According to these results, 2,2′,2″,2‴-[(2,2′-bipyridine-6,6′-diyl)bis(methylenenitrilo)]tetrakis