Two-Exciton states in Cyanine Dimers on DNA Scaffolds

The control of intermolecular coupling is a pathway towards achieving highly efficient energy transport in artificial light-harvesting networks. Similar requirements are also needed for the design of molecular wires and logic structures within the field of molecular excitonics. Here we report on the creation of cyanine dye homodimers on DNA scaffolds. The DNA provides a backbone to precisely control dye placement through covalent attachment and thereby the coupling strength, allowing the absorption and emission properties of the resulting dimers to be tailored. Through this strategy, we are able to realize delocalized one- and two-exciton states, the later of which is a first for a DNA-scaffolded system. Such multi-exciton states hold promise for entangled photon emission and molecular logic gates. Both the one- and two-exciton states are well described by molecular exciton theory when electron-vibrational coupling is accounted for. We also address the impact of molecular motion on the dynamics of these states, and identify a path towards greater control of these properties.