Purines Bearing Phenanthroline or Bipyridine Ligands and Their Ru ^II Complexes in Position 8 as Model Compounds for Electrochemical DNA Labeling – Synthesis, Crystal Structure, Electrochemistry, Quantum Chemical Calculations, Cytostatic and Antiviral Activity

Abstract A series of ethynyl‐ or (4‐boronophenyl)bipyridines and‐phenanthrolines were prepared as versatile building blocks for attachment of bidentate N‐ligands to other molecules via cross‐coupling reactions. Their complexation with Ru(bpy) 2 Cl 2 gave the corresponding Ru II complexes. 9‐Benzyladenine derivatives bearing the bipyridine or phenanthroline complexes in position 8, attached via a conjugate acetylene or phenylene linker were prepared by cross‐coupling reactions of the ethynyl‐ or 4‐boronophenylbipyridines and ‐phenanthrolines with 9‐benzyl‐8‐bromoadenine. Their complexation with Ru(bpy) 2 Cl 2 afforded the corresponding Ru complexes as model compounds for electrochemical DNA labeling. The same compounds were also prepared directly by cross‐coupling of 9‐benzyl‐8‐bromoadenine with Ru complexes of the alkynes and boronic acids. Both approaches are compared in terms of potential applications for labeling of nucleic acids. The crystal structures of two Ru complexes were determined by X‐ray diffraction. The electrochemistry of the model purines bearing the phenanthroline or bipyridine ligands and the Ru complexes was studied by means of cyclic or square‐wave voltammetry with carbon paste and mercury electrodes. The experimental redox potentials of the title compounds were compared with quantum chemical calculations. A very good agreement between experiment and theory was obtained, with a standard deviation of 0.13 V. It was shown that theoretical calculations can be of a limited predictive power for new Ru II complexes, though it was difficult to reproduce differences smaller than 0.05 V. Several compounds of this series exhibited a considerable cytostatic effect and activity against the hepatitis C virus (HCV). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)