Shining a New Light on an Old Game - An OsII-Based Near-IR Light Switch

We present a high-yield synthesis, the spectroscopic, electrochemical, and photophysical characterization of a new near-IR OsII DNA light switch based on the pydppz ligand {pydppz = 3-(pyrid-2'-yl)dipyrido[3,2-a:2',3'-c]phenazine}. The new compound represents, to the best of our knowledge, the first example of an [Os(tpy)2]-like species able to intercalate into DNA. This compound is completely quenched in aqueous solution and becomes luminescent in the near-IR spectral region in the presence of a small amount of biopolymer. Thus this osmium species behaves as a real OFF-ON DNA light switch.