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The first sequence-dependent study of DNA films containing metal-mediated base pairs was performed to investigate the charge transfer resistance (R ) of metal-modified DNA. The imidazole (Im) deoxyribonucleoside was chosen as a highly Ag -specific ligandoside for the formation of Im-Ag -Im complexes within the duplexes. This new class of site-specifically metal-modified DNA films was characterized by UV, circular dichroism (CD), and X-ray photoelectron spectroscopy (XPS). The electrochemical properties of these systems were investigated by means of electron impedance spectroscopy and scanning electrochemical microscopy. Taken together, these experiments indicated that the incorporation of Ag ions into the DNA films leads to reduced electron transfer through the DNA films. A simple device was proposed that can be switched reversibly between two distinct states with different charge transfer resistance.

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