24-karat DNA: Integrating tunable electronically delocalized coordination chains into discrete DNA duplexes

Biology’s information carrier, DNA, through its reliable synthesis, controllable length, and sequence-coded self-assembly, provides a unique capability for molecular-material/-device design. However, the intrinsic lack of tunable optoelectronics associated, generally, with delocalized electronic structures means it commonly acts in a passive role to organize “functional” components. The introduction of metal ions into duplex DNA to overcome this limitation has been widely explored, but, to date, the demonstration of such electronically delocalized motifs has proved elusive. Here, we incorporate Au(I)-thionate coordination chains into discrete duplex-DNA molecules by substituting native guanosine with the sulfur-modified analog, 6-thioguanosine. The resulting “24-karat DNA” displays the associated photoluminescence of the metallo chain, along with chiro-optical properties indicating this is conformationally flexible, adopting a duplex-matching helical arrangement. Furthermore, due to the electronic delocalization in the coordination chain, these features can be modulated by a simple extension of the thioG-sequence and {μS-Au-}n chain length and so provide a new tunability to the electronic structure of DNA-based architectures.