Octahedral ruthenium complexes with a dipyridophenazine ligand are synthetic DNA intercalators. Thanks to unique photophysical properties, they emit strong luminescence following binding to double strand DNA, particularly in the presence of mismatches. These compounds are thus potential diagnostic tools to detect DNA mutations.

Structural understanding of their binding mode to the DNA comes from crystallographic studies performed by Hang Song and colleagues, California Institute of Technology, USA, and Hakan Niyazi, University of Reading, UK, and coworkers.
The two groups examined the interactions between two different ruthenium complexes and oligomeric DNA duplex either bearing mismatches or free of them. In both cases the interactions were shown to unexpectedly occur through DNA’s minor groove.

• Crystal structure of Δ-[Ru(bpy)₂dppz]²⁺ bound to mismatched DNA reveals side-by-side metalloinsertion and intercalation,
  H. Song, J. T. Kaiser, J. K. Barton,
  Nature Chem. 2012, 4 (8), 615-619.
  DOI: 10.1038/nchem.1375
• Crystal structures of Λ-[Ru(phen)₂dppz]²⁺ with oligonucleotides containing TA/TA and AT/AT steps show two intercalation mode,
  H. Niyazi, J. P. Hall, K. O’Sullivan, G. Winter, T. Sorensen, J. M. Kelly, C. J. Cardin
  Nature Chem. 2012, 4 (8), 621-628.
  DOI: 10.1038/nchem.1397