First Examples of Luminescent Cyclometalated Iridium(III) Complexes as Labeling Reagents for Biological Substrates

The syntheses, and photophysical and electrochemical properties of the three luminescent cyclometalated iridium(III) complexes [Ir(ppy) 2 (phen-NCS)](PF 6 ) ( 1 ), [Ir(ppy) 2 (phen-NHCOCH 2 I)](PF 6 ) ( 2 ), and [Ir(ppy) 2 (phen-NH 2 )](PF 6 ) ( 3 ) (ppy - = 2-phenylpyridinate anion, phen-NCS = 5-isothiocyanato-1,10-phenanthroline, phen-NHCOCH 2 I = 5-(iodoacetamido)-1,10-phenanthroline, phen-NH 2 = 5-amino-1,10-phenanthroline) are reported. Since the isothiocyanate and iodoacetamide groups can react with the primary amine and sulfhydryl groups of biomolecules, respectively, complexes 1 and 2 have been used to label amine- or sulfhydryl-modified oligonucleotides, and human serum albumin, to give luminescent bioconjugates.