Conductance of alkyl-based molecules with one, two and three chains measured by electrochemical STM break junction

•Conductance of molecules with parallel alkyl chains is measured by ECSTM-BJ.•Conductance ratio between molecules with one and two chains is found more than twice.•Conductance of molecule with three chains is smaller than that with two chains.•Molecule with two chains may have constructive quantum interference.•Molecule with three chains may have destructive quantum interference.

In this communication, the conductance of molecules with one, two and three parallel alkyl chains was measured by electrochemical STM break junction approach. The conductance ratio between trans-1,4-cyclohexanedicarboxylic acid (M2) and 1,4-butanedicarboxylic acid (M1) is 2.4 for Ag and 2.5 for Cu electrodes. This may be contributed to the constructive quantum interference in M2 molecule with two parallel chains. However, the conductance of bicyclo[2.2.2]octane-1,4-dicarboxylic acid (M3) with three parallel alkyl chains is smaller than that of M2, which may arise from the destructive quantum interference when electron transport through M3. The current work reveals the interference effect in the alkyl molecule, and proposes a feasible way to design high performable molecule wires.