Interaction of mononuclear nickel(II) enantiomers, Δ- and Λ-bis(1,10-phenanthroline) (dipyrido[3,2-a:2′,3′-c]phenazine)nickel(II) chloride, with calf thymus DNA

Circular dichroism (CD) spectroscopy was used to investigate the interaction of Δ- and Λ-enantiomers of a mononuclear Ni(II) complex, [Ni(phen)2(dppz)]2+ (where phen = 1,10-phenanthroline and dppz = dipyrido[3,2-a:2′,3′-c]phenazine), with CT-DNA. The pure Ni(II) enantiomers were synthesized via a chiral precursor. The changes in the absorption and CD spectra upon binding provide detailed information about DNA binding of the enantiomers. The change in the CD spectra over time was used to calculate the racemization rates in the absence and presence of DNA. It was observed that the Δ-enantiomer racemizes slower than the Λ-enantiomer in the presence of DNA. Competition between the Ru(II) enantiomers, Δ- and Λ-[Ru(phen)2(dppz)]2+, and the Ni(II) enantiomers, Δ- and Λ-[Ni(phen)2(dppz)]2+, was also studied via luminescence titration.