A range of chiral building blocks of the type Δ‐ or Λ‐[Ru(pp)2(CO)2]2+ {pp = bidentate ligands bpy (2,2′‐bipyridine), phen (1,10‐phenanthroline) and Me2bpy (4,4′‐dimethyl‐2,2′‐bipyridine)} have been synthesized, and their enantiomeric purity and absolute configurations determined by CD and NMR studies. Decarbonylation using trimethylamine oxide in the presence of the respective pp ligand at room temperature produced the corresponding tris(bidentate) species [Ru(pp)3]2+ with retention of configuration at the ruthenium(II) centre. A general chromatographic technique for resolution of tris‐homoleptic complexes of the type [Ru(pp)3]2+ was investigated, with the absolute configurations of the resolved complexes confirmed by CD studies, and the X‐ray structural analyses of Δ‐(–)‐[Ru(Me2bpy)3]{(–)‐O,O′‐dibenzoyl‐L‐tartrate} and Λ‐(+)‐[Ru(phen)3]{(+)‐O,O′‐di‐4‐toluoyl‐D‐tartrate}. Resolution is also reported for the analogous species containing three potential bridging ligands, [Ru(bpm)3]2+ and [Ru(HAT)3]2+ (bpm = 2,2′‐bipyrimidine; HAT = 1,4,5,8,9,12‐hexaazatriphenylene). The versatility of the chromatographic procedure was demonstrated by the resolution of a series of bis‐heteroleptic complexes [Ru(pp)2(pp′)]2+ {pp′ = dpq (dipyrido[3,2‐d:2,3′‐f]quinoxaline), dpqc (dipyrido[3,2‐a:2,3‐d]‐6,7,8,9‐tetrahydrophenazine), and dppz {dipyrido[3,2‐a:2,3′‐d]phenazine)}.

1H NMR spectroscopy and viscosity measurements have been used to study the oligonucleotide binding of the Delta- and Lambda-enantiomers of the metal complex [Ru(dmphen)(2)dpq](2+) (dmphen = 2,9-dimethyl-1,10-phenanthroline and dpq = dipyrido[3,2-f:2',3'-h]quinoxaline). The addition of either enantiomer to d(GTCGAC)(2) induced large upfield shifts and significant broadening for the hexanucleotide imino and metal complex dpq resonances. These data coupled with the observed increase in the melting transition midpoint of the hexanucleotide duplex upon addition of either enantiomer suggests that both Delta- and Lambda-[Ru(dmphen)(2)dpq](2+) bind by intercalation. A significant number of metal complex to hexanucleotide NOE contacts were observed in NOESY spectra of d(GTCGAC)(2) with added Delta- or Lambda-[Ru(dmphen)(2)dpq](2+). The observed intermolecular NOEs were consistent with both enantiomers intercalating between the G(4)A(5) bases of one strand and the T(2)C(3) bases of the complementary strand. Intermolecular NOEs from the dmphen protons were only observed to protons located in the hexanucleotide minor groove. Alternatively, NOE contacts from the dpq protons were observed to both major and minor groove protons. The NOE data suggest that the dpq ligand of the Delta-enantiomer intercalates deeply into the hexanucleotide base stack while the Lambda-enantiomer can only partially intercalate. Viscosity measurements were consistent with the proposed intercalation binding models. The addition of the Delta-enantiomer increased the relative viscosity of the DNA solution, while a decrease in the relative viscosity of the DNA was observed upon addition of the Lambda-metal complex. These results confirm our proposal that octahedral metallointercalators can intercalate from the minor groove. In addition, the results demonstrate that the left-handed enantiomer of [Ru(dmphen)(2)dpq](2+) prefers to intercalate from the narrow minor groove despite only being able to partially insert a polycyclic aromatic ligand into the DNA base stack.

No abstract