Tuning the Excited State of Water‐Soluble Ir^III‐Based DNA Intercalators that are Isostructural with [Ru^II(NN)₂(dppz)] Light‐Switch Complexes

Abstract

Abstract The synthesis of two new Ir III complexes which are effectively isostructural with well‐established [Ru(NN) 2 (dppz)] 2+ systems is reported (dppz=dipyridophenazine; NN=2,2′‐bipyridyl, or 1,10‐phenanthroline). One of these Ir III complexes is tricationic and has a conventional N 6 coordination sphere. The second dicationic complex has a N 5 C coordination sphere, incorporating a cyclometalated analogue of the dppz ligand. Both complexes show good water solubility. Experimental and computational studies show that the photoexcited states of the two complexes are very different from each other and also differ from their Ru II analogues. Both of the complexes bind to duplex DNA with affinities that are two orders of magnitude higher than previously reported Ir(dppz)‐based systems and are comparable with Ru II (dppz) analogues.