DNA Interactions of a Dinuclear Ruthenium(II) Complex Bridged by 1,3-bis(1,10-phenanthroline[5,6-d]imidazol-2-yl)benzene

Abstract

A novel dinuclear ruthenium(II) complex [(phen) 2 Ru(mbpibH 2 )Ru(phen) 2 ] 4+ [phen=1,10-phenanthroline; mbpibH 2 =1,3-bis(1,10-phenanthroline[5,6-d]imidazol-2-yl)-benzene] has been synthesized and characterized. The DNA-binding behavior of this complex has been studied by spectroscopic and viscosity measurements. Results suggest that the dinuclear ruthenium(II) complex intercalates into DNA base pairs via its bridging moiety. It has also been found that the dinuclear ruthenium(II) complex displays the enantiopreferential DNA-binding after equilibrium dialysis.

AT‐Specific DNA Binding of Binuclear Ruthenium Complexes at the Border of Threading Intercalation

“…[5] Based on viscosity experiments and the fact that the intraA C H T U N G T R E N N U N G liA C H T U N G T R E N N U N G gand absorption bands in the UV region showed much greater hypochromicity than the MLCT bands in the visible region upon addition of ct-DNA to the complex, Chao et al proposed that it is the bridging ligand that interacts with the DNA and that the binding mode is intercalation rather than partial intercalation. However, classic intercalation would, contrary to what was observed in our experiments, be expected to result in good orientation of the DNA in the LD experiments as a result of stiffening and lengthening of the helix upon insertion of the ligand between the base pairs.…”

“…Complex 2 exhibits luminescence in aqueous solution with a maximum at around 600 nm when excited at 460 nm, as reported previously. [5] In acetonitrile, the complex shows luminescence with a similar intensity to that in water, but the maximum is slightly redshifted. When excited at 460 nm, 3 shows no luminescence in water but exhibits strong emission at around 680 nm in acetonitrile.…”

“…[1][2][3] However, the majority of these studies have concerned mononuclear complexes and only recently have binuclear ruthenium complexes, which in general show greater selectivity due to increased size and higher binding affinity due to increased charge, started to receive attention. [4][5][6][7] Of these, the semi-rigid binuclear ruthenium complex [mbidppzA C H T U N G T R E N N U N G (phen) 4 Ru 2 ]…”

“…[28] Chao et al have previously reported the synthesis and DNA-binding studies of racemic [m-bipbA C H T U N G T R E N N U N G (phen) 4 Ru 2 ] ,10]phenanthrolin-2-yl)benzene), [5] complex 2 in Scheme 1, which is of a similar overall size to 1 but has a bridging ligand that is expected to be more flexible due to the two pivotal single bonds. It has been reported to interact with calf thymus DNA by intercalation of the bridging ligand.…”

“…Because the threading intercalation kinetics of complex 1 have been found to be sensitive to the chirality of ruthenium coordination [12] and dialysis experiments with racemic complex 2 have revealed enantioselective binding, [5] the pure enantiomers of complexes 2 and 3 were synthesised and studied in this work.…”