Exploitation of Luminescent Transition Metal Polypyridine Complexes as Bioorthogonal Probes, Cellular Imaging Reagents, and Photocytotoxic Agents

There has been a long-standing interest in the interactions of transition metal complexes with biological molecules. However, the design of luminescent transition metal complexes as biomolecular probes, bioimaging reagents, and photocytotoxic agents has not been focused upon until recently. In particular, the interesting photophysical and photochemical properties of rhenium(I), ruthenium(II), and iridium(III) polypyridine complexes have prompted us to develop cellular reagents with diagnostic and therapeutic potential. Thus, we have modified these metal complexes with different functional units such as poly(ethylene glycol), 2-nitrobenzyl, cyclooctyne, tetrazine, nitrone, and sydnone. These groups not only perturb the emission properties of the complexes, but also allow the complexes to establish specific biological recognition capability. In this lecture, our recent work on the applications of luminescent rhenium(I), ruthenium(II), and iridium(III) polypyridine complexes as cellular reagents will be described. Our focus will be on the photophysical and photochemical properties, bioorthogonal labeling, cellular uptake, and photocytotoxic activity of these photofunctional transition metal complexes.