We have designed and synthesized five azulene derivatives containing gold-binding groups at different points of connectivity within the azulene core toprobe the effects of quantum interference through single-molecule conductancemeasurements. We compare conducting paths through the 5-membered ring,7-membered ring, and across the long axis of azulene. We find that changing thepoints of connectivity in the azulene impacts the optical properties (asdetermined from UV-Vis absorption spectra) and the conductivity. Importantly,we show here that simple models cannot be used to predict quantum interferencecharacteristics of non-alternant hydrocarbons. As an exemplary case, we showthat azulene derivatives that are predicted to exhibit destructive interferencebased on widely accepted atom-counting models show a significant conductance atlow biases. Although simple models to predict the low-bias conductance do nothold with all azulene derivatives, we show that the measured conductance trendfor all molecules studied actually agrees with predictions based on the morecomplete GW calculations for model systems.
展开▼
