Substituted dipyridophenazine complexes of Cr(III): Synthesis, enantiomeric resolution and binding interactions with calf thymus DNA

[Cr(phen)(2)(X(2)dppz)](3+) {X = H, Me, or F} have been synthesised, characterised, and chromatographically resolved into their constituent Delta and Lambda enantiomers. The DNA-binding interactions of each of the racemic complexes were investigated, with the results of linear dichroism, thermal denaturation, and emission quenching studies indicative of intercalative binding to CT-DNA with a significant electrostatic contribution. UV/Vis absorption titrations suggest strong DNA binding by each of the racemic complexes, with the methylated analogue [Cr(phen)(2)(Me(2)dppz)](3+) exhibiting the largest equilibrium binding constant. Emission quenching and UV-Vis titrations of the enantiomers of [Cr(phen)(2)(dppz)](3+) imply similar binding affinities for the Delta and Lambda isomers, although significant differences between the circular dichroism spectra of the enantiomers in the presence of DNA connote differences in binding orientation and/or conformation between the two.