Length-dependent conductance of conjugated molecular wires synthesized by stepwise "click" chemistry.

We report the preparation and electrical characterization of conjugated oligophenylenetriazole (OPT) wires having systematically varied lengths up to 10 nm. OPT wires were built from gold substrates using Cu(I)-catalyzed azide alkyne cycloaddition and characterized comprehensively by RAIRS, ellipsometry, and XPS. We observed a clear transition in direct current (DC) transport from tunneling to hopping in a length range between 4 and 5 nm as previously established for oligoarylimine wires. Stepwise click cycloaddition represents a new efficient method to prepare long conjugated molecular wire self-assembled monolayers (SAMs) on Au surfaces for conduction measurements and is expected to be compatible with a variety of functionalities and bonding architectures in the wire backbones.