X‑ray Crystal Structure of <i>rac-</i>[Ru(phen)₂dppz]²⁺ with d(ATGCAT)₂ Shows Enantiomer Orientations and Water Ordering

We report an atomic resolution X-ray crystal structure containing both enantiomers of rac-[Ru­(phen)2dppz]2+ with the d­(ATGCAT)2 DNA duplex (phen = phenanthroline; dppz = dipyridophenazine). The first example of any enantiomeric pair crystallized with a DNA duplex shows different orientations of the Λ and Δ binding sites, separated by a clearly defined structured water monolayer. Job plots show that the same species is present in solution. Each enantiomer is bound at a TG/CA step and shows intercalation from the minor groove. One water molecule is directly located on one phenazine N atom in the Δ-enantiomer only.