[Ru(TAP)₂(dppz)]²⁺: a DNA intercalating complex, which luminesces strongly in water and undergoes photo-induced proton-coupled electron transfer with guanosine-5′-monophosphate

Abstract

The lowest excited state of [Ru(TAP)2(dppz)]2+ (TAP = 1,4,5,8-tetraazaphenanthrene, dppz = dipyrido[3,2-a:2',3'-c]phenazine) 1 is strongly luminescent, even in water, and very oxidizing. Therefore it is able to oxidise not only guanosine-5'-monophosphate (GMP), as demonstrated by laser flash photolysis, but also guanine-containing polynucleotides such as calf thymus DNA and [poly(dG-dC)]2. The luminescence quenching was found to be faster in H2O than in D2O, as is the back reaction, indicating that both processes probably proceed by proton-coupled electron transfer. These properties, that are controlled by the triplet MLCT state in which the charge has been transferred from the Ru to a TAP ligand, contrast with those of the well known [Ru(phen)2(dppz)]2+ 2.

Reversal of a Single Base‐Pair Step Controls Guanine Photo‐Oxidation by an Intercalating Ruthenium(II) Dipyridophenazine Complex

“…This observation may be contrasted with studies on tethered intercalators, where it was found that the ET yield, though not necessarily the rate, was affected by distance 3b. This may suggest the involvement of different mechanisms in our case, such as proton‐coupled ET 7b,c. Our experiments are consistent with the reactive excited state being a triplet ML(TAP)CT species, although a role for triplet ππ* state, as suggested by recent computational studies4 (and experiments on related systems)15 cannot be excluded.…”

“…However, it may be noted that this lifetime is shorter than that for the excited state of [Ru(TAP) 2 (dppz)] 2+ either unbound (1080 ns) or bound to a duplex that does not contain G (e.g. poly{dA‐dT} 2 ; τ =1580 ns) 7b. This implies that excited‐state quenching occurs, but with a much lower rate than in A .…”

Structure determination of an intercalating ruthenium dipyridophenazine complex which kinks DNA by semiintercalation of a tetraazaphenanthrene ligand

“…Rac-½RuðTAPÞ 2 ðdppzÞCl 2 was prepared by a modification of the literature method (40). The two enantiomers were successfully resolved by introducing an aqueous solution of rac-½RuðTAPÞ 2 ðdppzÞCl 2 onto a Sephadex C-25 column with 0.1 M (-)-O, O′-dibenzoyl-L-tartrate as the eluent at 2 mL∕ min flow rate recycled by a peristaltic pump (23).…”

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

“…For instance it is often possible to select a complex with an excited state having an appropriate redox potential or one which shows exquisite sensitivity to its environment. [10][11][12][13][14][15][16][17][18] These properties are particularly valuable for potential therapeutic and diagnostic applications involving the interaction of such complexes with nucleic acids or proteins. [19][20] For example, directed photooxidative damage of nucleic acids opens the possibility of designing a new class of selective antitumour drugs.…”