As eries of new Ru II Schiff base complexes built on the salphen moiety has been prepared. Thisi ncludes four flexible monometallic Ru II compounds and six rigid bimetallic analogues that contain Ni II ,P d II or Pt II cations into the salphen complexation site. Steadys tate luminescence titrations illustrated the capacity of the compounds to photoprobe Gquadruplex (G4) DNA.M oreover,t he vast array of the Schiff base structuralc hangesa llowed to extensivelya ssess the influenceo fthe ligand surface, flexibility and chargeont he interaction of the compounds with G4 DNA. This was achieved thanks to circulard ichroism melting assays and bio-layer interferometry studies that pointed up high affinities along with good selectivities of Ru II Schiff base complexes for G4 DNA. In cellulo studiesw ere carriedo ut with the most promising compounds. Cellular uptake with location of the compounds in the nucleus as well as in the nucleolus was observed. Cell viability experiments were performed with U2OS osteosarcomac ellsi nt he dark and under light irradiation which allowed the measurements of IC 50 values and photoindexes.T heys howedt he substantial role played by light irradiation in the activity of the drugsi na ddition to the low cytotoxicity of the molecules in the dark. Altogether,t he reportedr esults emphasize the promising propertieso fR u II Schiffbase complexesasanew class of candidates for developing potentialG 4D NA targeting diagnostic or therapeutic compounds.

Favored radiative deactivation processes in dissymmetric Ru(ii) complexes enable photodetection of DNA mismatches.

Novel dinuclear ruthenium(ii) complexes were designed to target and to photo-react with G-quadruplex telomeric DNA. Thanks to a microscopic-based telomere dysfunction assay, we brought the first evidence of G-driven telomeric DNA photo-lesions in cellulo.