Homo- and Heterobimetallic Ruthenium(II) and Osmium(II) Complexes Based on a Pyrene-Biimidazolate Spacer as Efficient DNA-Binding Probes in the Near-Infrared Domain

Abstract

We report in this work a new family of homo- and heterobimetallic complexes of the type [(bpy)2M(Py-Biimz)M'(II)(bpy)2](2+) (M = M' = Ru(II) or Os(II); M = Ru(II) and M' = Os(II)) derived from a pyrenyl-biimidazole-based bridge, 2-imidazolylpyreno[4,5-d]imidazole (Py-BiimzH2). The homobimetallic Ru(II) and Os(II) complexes were found to crystallize in monoclinic form with space group P21/n. All the complexes exhibit strong absorptions throughout the entire UV-vis region and also exhibit luminescence at room temperature. For osmium-containing complexes (2 and 3) both the absorption and emission band stretched up to the NIR region and thus afford more biofriendly conditions for probable applications in infrared imaging and phototherapeutic studies. Detailed luminescence studies indicate that the emission originates from the respective (3)MLCT excited state mainly centered in the [M(bpy)2](2+) moiety of the complexes and is only slightly affected by the pyrene moiety. The bimetallic complexes show two successive one-electron reversible metal-centered oxidations in the positive potential window and several reduction processes in the negative potential window. An efficient intramolecular electronic energy transfer is found to occur from the Ru center to the Os-based component in the heterometallic dyad. The binding studies of the complexes with DNA were thoroughly studied through different spectroscopic techniques such as UV-vis absorption, steady-state and time-resolved emission, circular dichroism, and relative DNA binding study using ethidium bromide. The intercalative mode of binding was suggested to be operative in all cases. Finally, computational studies employing DFT and TD-DFT were also carried out to interpret the experimentally observed absorption and emission bands of the complexes.

Induction of C-Myc G-Quadruplex Dna and Cytotoxicity of a Calix[]arene-Containing Binuclear Ruthenium(ii) Complex

“…This phenomenon is similar to that observed for [(phen)2Ru(bpibp)Ru(phen)2](ClO4)4 which has been shown to be groove binding to c-myc G-quadruplex DNA [29]. The DNA binding affinity of the complex can be evaluated quantitatively by monitoring the increasing of the emission dates in luminescence titration according to Bard-Torp-Murphy equations [34]. As shown in Fig.…”

Synthesis, photophysical, electrochemical and DNA binding properties of a novel ruthenium(II) N^N complex

“…S.C.E., and the reduction E ½ are -1.08 6 and are typical of these systems. Based on the previous assignment on the reduction peaks of ruthenium(II) N^N complexes, 9 the reduction couples at -1.08 V vs. S.C.E. are assigned as the reduction of the N^N ligands, which are similar to those found in [Ru(bpy) 2 (diN)] 2+ (ca.…”

A Promising Dna Groove Binder and Photocleaver Based on a Dinuclear Ruthenium(ii) Complex

“…As well known, the free EB in aqueous solution is very weakly emissive because the surrounding water molecules quench its fluorescence. [38,40] However, the fluorescence of EB would be sharply increased by a factor of 20 after binding to DNA with two modes, namely intercalation and groove binding. It was previously reported that the enhanced fluorescence of the DNA-EB complex could be quenched by the addition of a second DNA binder which is either an intercalator or a groove binder, such as intercalators of [Ru 2 (bpy) 4 L] 4+ [11] and groove binder of [Ru(phen) 2 (Hcdpq)] 2+ .…”

“…in which K app is the apparent DNA binding constant of the ruthenium complex, K EB is the DNA binding constant of EB, [EB] 50% and [Ru] 50% are the EB and ruthenium complex concentrations at 50% EB replacement. [38,40] The inset of Fig. S2 revealed that 50% of EB molecules were displaced by the complex at a concentration ratio of [Ru]/[EB] = 0.46 (the influence of ruthenium complex at 537 nm was subtracted already).…”