Abstract
In this work, the conductance of molecules with different alkyl length between benzene and carboxylic acid at each side are explored by electrochemical jump-to-contact STM break junction. The results show that the quantum interference (QI) is found in meta-phenylenedipropionic acid containing two methylene groups between benzene ring and carboxylic acid, and there is no obvious QI effect for meta-phthalic acid and meta-phenylenediacetic acid with shorter alkyl between benzene and carboxylic acid. We attribute the disappearance of the QI in meta-phthalic acid and meta-phenylenediacetic acid to the strong interaction between the benzene ring and anchoring group when they are too close. The current result reveals the importance role of alkyl chain on benzene ring and anchoring group in QI effect.
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•Quantum interference effect (QI) of carboxylic acid-based molecules was investigated.•Conductance of carboxylic acid molecules were measured by electrochemical STM-BJ.•QI is found for phenylenedipropionic acid.•No obvious QI is found for phthalic acid and phenylenediacetic acid.•The QI is influence by the interaction between benzene ring and anchoring group.