Interaction of Ruthenium(II)‐dipyridophenazine Complexes with CT‐DNA: Effects of the Polythioether Ancillary Ligands

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Abstract
The complexes [Ru([9]aneS3)(dppz)Cl]Cl 1 and [Ru([12]aneS4)(dppz)]Cl2,2 ([9]aneS3 = 1,4,7‐ trithiaciclononane and [12]aneS4 = 1,4,7,10‐tetrathiaciclododecane) were synthesised and fully characterised . These complexes belong to a small family of dipyridophenazine complexes with non‐polypyridyl ancillary ligands . Interaction studies of these complexes with CT‐DNA (UV/Vis titrations, steady‐state emission and thermal denaturation) revealed their high affinity for DNA . Intercalation constants determined by UV/Vis titrations are of the same order of magnitude (106) as other dppz metallointercalators, namely [Ru(II)(bpy)2dppz]S2+. Differences between l and2 were identified by steady‐state emission and thermal denaturation studies . Emission results are in accordance with structural data, which indicate how geometric distortions and different donor and/or acceptor ligand abilities affect luminescence . The possibility of noncovalent interactions between ancillary ligands and nucleobases by van der Waals contacts and H‐bridges is discussed . Furthermore, complex l undergoes aquation under intra‐cellular conditions and an equilibrium with the aquated form l′ is attained . This behaviour may increase the diversity of available interaction modes.

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