Abstract
A key area of activity in contemporary molecular electronics is the chemical control of conductance of molecular junctions and devices. Here we study and modify a range of pyrrolodipyridines (carbazole-like) molecular wires. We are able to change the electrical conductance and quantum interference patterns by chemically regulating the bridging nitrogen atom in the tricyclic ring system. A series of eight different N-substituted pyrrolodipyridines has been synthesized and subjected to single-molecule electrical characterization using an STM break junction. Correlations of these experimental data with theoretical calculations underline the importance of the pyrrolic nitrogen in facilitating conductance across the molecular bridge and controlling quantum interference. The large chemical modulation for the meta-connected series is not apparent for the para-series, showing the competition between (i) meta-connectivity quantum interference phenomena and (ii) the ability of the pyrrolic nitrogen to facilitate conductance, that can be modulated by chemical substitution.
Highlights
I n recent years, quantum interference has been one of the most actively pursued topics in molecular electronics
Quantum interference (QI) has been demonstrated across a wide range of molecules either as multi- or monolayer films sandwiched between pairs of conductors or as single molecules bridging between nanoelectrode pairs
In the former case, it has been shown through direct twoterminal electrical measurements across self-assembled monolayers that QI is sensitive to chemical changes and conjugation patterns.[1,2]
Summary
I n recent years, quantum interference has been one of the most actively pursued topics in molecular electronics. In the former case, it has been shown through direct twoterminal electrical measurements across self-assembled monolayers that QI is sensitive to chemical changes and conjugation patterns.[1,2] Conjugation has been used as one of the primary ways of controlling quantum interference, with a classic exemplar being para- versus meta-substitution in a central benzene ring in a molecular wire.
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