DNA interaction with dipolar ruthenium(II) ammine complexes containing 4,4′-bipyridinium as photochemotherapeutic agents

•DNA interaction with dipolar ruthenium(II) complexes has been investigated.•The complexes involve strong stacking interactions of L+ with DNA duplex.•The complexes can function as O2-independent photochemotherapeutic agents.

The interaction of DNA with dipolar ruthenium(II) ammine complexes containing 4,4′-bipyridinium cations L+, [Ru(L+)(NH3)5]3+, has been investigated by spectroscopic and electrochemical methods. These ruthenium(II) complexes undergo strong stacking interactions of L+ with the base-pairs of DNA duplex in addition to the electrostatic and hydrogen binding modes. The phbp+ ([2]3+) and pymbp+ ([3]3+) complexes bind to DNA more strongly than the mebp+ ([1]3+) complex, due to the presence of extended planar aromatic ligands. [3]3+ which exhibited the strongest interaction with DNA can bind to supercoiled plasmid pBR322 DNA following photoinduced loss of ligands pymbp+ and NH3. The finding led to the photocleavage of supercoiled plasmid pBR322 DNA by [3]3+ with visible light under aerobic and unaerobic conditions. Since similar photolysis of [1]3+ and [2]3+ has been observed, all the dipolar ruthenium(II) ammine complexes bearing 4,4′-bipyridinium cations can function as O2-independent photochemotherapeutic agents.

Graphical abstractDipolar ruthenium(II) ammine complexes containing 4,4′-bipyridinium cations L+, [Ru(L+)(NH3)5]3+, can bind to supercoiled plasmid pBR322 DNA following photoinduced ligand loss, L+ and NH3. These complexes can function as O2-independent photochemotherapeutic agents.Figure optionsDownload full-size imageDownload as PowerPoint slide