Dipyrido[3,2-a:2′,3′-c]quinolino[3,2-j]phenazine (dpqp-OH) – Synthesis, characterization and DNA interaction of the corresponding Ru(II) complex

Synthesis of three series of ruthenium tris-diimine complexes containing acridine-based π-extended ligands using an efficient “chemistry on the complex” approach

Novel multi-step chemistry on the complex strategy.

Effect of ancillary ligands on the DNA interaction of [Cr(diimine)3]3+ complexes containing the intercalating dipyridophenazine ligand

The synthesis of photoluminescent Cr(III) complexes of the type [Cr(diimine)(2)(DPPZ)](3+) are described, where DPPZ is the intercalating dipyridophenazine ligand, and diimine corresponds to the ancillary ligands bpy, phen, DMP, and TMP (where bpy = 2,2'-bipyridine, phen = 1,10-phenanthroline, DMP = 5,6-dimethyl-1,10-phenanthroline, and TMP = 3,4,7,8-tetramethyl-1,10-phenanthroline). For TMP, DMP, and phen as ancillary ligands, the complexes have also been resolved into their Lambda and Delta optical isomers. A comparison of the photophysical and electrochemical properties reveal similar (2)E(g) --> (4)A(2g) (O(h)) emission wavelengths and lifetimes, and a variation of 110 mV in the (2)E(g) excited state oxidizing power. A detailed investigation has been undertaken of ancillary ligand effects on the DNA binding of these complexes with a range of polynucleotides. For all four complexes, emission is quenched by the addition of calf thymus B-DNA, with the emission lifetime data yielding bimolecular quenching rate constants close to the diffusion controlled limit. Equilibrium dialysis studies have established a general predilection for AT base binding sites, while companion experiments with added distamycin (a selective minor groove binder) provide evidence for a minor groove binding preference. For the case of [Cr(TMP)(2)(DPPZ)](3+), concomitant equilibrium dialysis and circular dichroism measurements have demonstrated very strong enantioselective binding by the Lambda optical isomer. The thermodynamics of DNA binding have also been explored via isothermal titration calorimetry (ITC). The ITC data establish that the primary binding mode for all four Cr(III) complexes is entropically driven, a result that is attributed to the highly favorable free energy contribution associated with the hydrophobic transfer of the Cr(III) complexes from solution into the DNA binding site.

Synthesis, Characterization, DNA Binding, and Photocleavage of [Ru(bpy)2(MFIP)]2+ and [Ru(phen)2(MFIP)]2+

The new ligand 2-(5-methyl-furan-2-yl)imidazo[4,5-f][1, 10]phenanthroline (MFIP) and its complexes [Ru(bpy)2(MFIP)]2+ 1 (bpy = 2,2′-bipyridine) and [Ru(phen)2(MFIP)]2+ 2 (phen = 1,10-phenanthroline) were synthesized and characterized by elemental analysis, mass spectrometry, and 1H NMR spectroscopy. The DNA binding properties of the two complexes were investigated by different spectrophotometric methods and viscosity measurements. The results suggest that both complexes bind to calf thymus DNA (CT-DNA) through intercalation, and both complexes can enantioselectively interact with CT-DNA. The Λ enantiomers of both complexes are slightly predominant for binding to CT-DNA over the Δ enantiomer. When irradiated at 400 nm, the two complexes promote the photocleavage of pBR322 DNA, and complex 2 cleaves DNA more effectively than complex 1 under comparable experimental conditions. Furthermore, mechanism studies reveal that singlet oxygen (1O2) plays a significant role in the photocleavage.