Utilization of Rhenium(I) Polypyridine Complexes Featuring a Dinitrophenylsulfonamide Moiety as Biothiol‐Selective Phosphorogenic Bioimaging Reagents and Photocytotoxic Agents

We report herein a series of rhenium(I) polypyridine complexes featuring a 2,4‐dinitrophenylsulfonamide (DNPS) unit as phosphorogenic bioimaging reagents and photocytotoxic agents. The biothiol‐selective rhenium(I) polypyridine complexes [Re(N^N)(CO)3(py‐DNPS)](CF3SO3) (py‐DNPS=3‐((2,4‐dinitrophenylsulfonyl)aminomethyl)pyridine) and their DNPS‐free counterparts [Re(N^N)(CO)3(pyridine)](CF3SO3) were synthesized and characterized. Upon photoexcitation, the DNPS complexes exhibited very weak luminescence as a result of photoinduced electron transfer (PET) from the excited rhenium(I) diimine moiety to the DNPS quenching unit. However, upon treatment with glutathione (GSH), the DNPS moiety was removed, resulting in emission enhancement of the solutions (I/Io=12.6–22.2). After reaction of the DNPS complexes with GSH in living cells, intense intracellular emission and potent photocytotoxicity were both observed. Additionally, the modification of the diimine ligand with a tosylamide unit conferred on the complexes an endoplasmic reticulum (ER)‐targeting ability, which can be exploited for selective bioimaging and photocytotoxic applications. The 2,4‐dinitrophenylsulfonamide (DNPS) moiety was utilized as both an emission quencher and a GSH‐responsive functional group in rhenium(I) polypyridine complexes. Due to the selective emission turn‐on upon reaction with GSH, the complexes were utilized in phosphorogenic bioimaging and photocytotoxic applications.