Interaction of Cr(diimine)₃³⁺ Complexes with DNA

Abstract

Luminescence spectroscopy coupled with capillary electrophoresis (CE) provides insight into the nature and stereoselectivity of Cr(diimine)3 3+ interactions with polynucleotides. Photoluminescence measurements on Cr(phen)3 3+ and Cr(bpy)3 3+ in air or N2-saturated solution demonstrate strong B-DNA quenching of Cr(diimine)3 3+ emission intensities and lifetimes. Both dynamic and static quenching are observed, the latter being attributed to DNA bound Cr(diimine)3 3+. Very rapid quenching is also observed with deoxyguanosine monophosphate (dGMP), while no bimolecular quenching is observed with other mononucleotides. Likewise, poly(dG-dC)·poly(dG-dC) causes rapid quenching, while only minor quenching is observed for poly(dA-dT)·poly(dA-dT). These emission results are consistent with a DNA quenching mechanism involving guanine base oxidation. The electropherogram resulting from the co-injection of rac-Cr(phen)3 3+ and rac-Ru(phen)3 2+ into a capillary containing B-DNA indicates a similar binding constant for the two complexes, while the enantiomeric stereoselectivities are reversed. CE studies for Ru(phen)3 2+ with distamycin A (an AT selective minor groove binder) reveal a significant reduction in complex migration times and a complete loss of enantiomeric discrimination. These results are consistent with a literature model where nonelectrostatic binding for both isomers occurs in the minor groove. Analogous distamycin studies with Cr(phen)3 3+ are also in accord with minor groove binding.

Excited state behaviour of substituted dipyridophenazine Cr(iii) complexes in the presence of nucleic acids

“…[24][25][26][27] More recently, chromium(III) complexes have also received attention, as these complexes (in which the central metal ion has a d3 configuration) exhibit long-lived, spectrally narrow room temperature phosphorescence and have strong excited state oxidizing power. [28][29] They are also water soluble and relatively non-labile, properties conducive to their application in biological systems. It should be emphasised that in contrast to the MLCT state of the analogous ruthenium complexes 26,[30][31] the lowest excited state of the [Cr(phen) 2 (X 2 dppz)] 3+ is metalcentred and luminescent in aqueous solution.…”

[Cr(ddpd)2]3+: A Molecular, Water‐Soluble, Highly NIR‐Emissive Ruby Analogue

“…[15] These experiments demonstrate the superior stability of 1 3+ compared to [Cr(bpy) 3 3+ photooxidize dGMP and hence,c leave DNAi n their excited states (ttpy = p-tolylterpyridine,dGMP = deoxyguanosine monophosphate). [31] Indeed, dGMP (E = 1.29 Vvs. NHE) quenches the emission of [Cr(bpy) 3 ] 3+ under our conditions but not that of 1 3+ ( Figure S19).…”

Capillary electrophoresis as a probe of enantiospecific interactions between photoactive transition metal complexes and DNA

“…1), and the stereospecificity of interaction with the chiral DNA backbone is well documented for several Tris-diimine-TM systems of d 6 electronic configuration [17][18][19][20][21]. In our own studies, we have recently reported on several [Cr(diimine) 3 ] 31 systems of d 3 -configuration where the oxidizing power of the 2 E g photoexcited state of Cr(III) results in the oxidation of the guanine base in DNA, leading to the potential for strand cleavage [22][23][24]. In design-…”