Point-to-point capture of DNA with the aid of intercalation by immobilized rod-shaped Ru complexes at solid surface towards nanowiring

Novel rod-shaped Ru complex having naphthalene-1, 4:5,8-bis(dicarboximide) (ndi) as a DNA intercalating group and alkylphosphonate as an anchoring group was synthesized. Upon addition of calf thymus DNA to aqueous solution of the Ru complex, both metal-to-ligand charge transfer (MLCT) bands at 491 nm and the π–π* (ndi) transition at 364 and 385 nm were shifted to longer wavelengths with decreasing their intensity, which strongly indicates that the Ru complex was intercalated into the double-stranded DNA base pairs. For the low coverage of the Ru complex immobilized on mica surface, λ-DNA was captured in a point-to-point manner by a meniscus transfer method. From the AFM measurements, the hydrohobicity/hydrophilicity of the mica surface affects the shape of the trapped DNA; i.e., the DNA was effectively straightened on the hydrophobic mica surface.