Single Molecule Conductance of Electroactive Helquats: Solvent Effect

• Published in: ChemElectroChem Vol. 6; no. 23; pp. 5856 - 5863
• Main Authors: Kolivoška, Viliam, Šebera, Jakub, Severa, Lukáš, Mészáros, Gábor, Sokolová, Romana, Gasior, Jindřich, Kocábová, Jana, Hamill, Joseph M., Pospíšil, Lubomír, Hromadová, Magdaléna
• Format: Journal Article
• Language: English
• Published: Weinheim John Wiley & Sons, Inc 02.12.2019
• Subjects: Anchoring; break junction methods; Electrochemical analysis; electrochemistry; helquats; Mesitylene; Polar environments; Resistance; single molecule conductance; Solvent effect; Solvents
• ISSN: 2196-0216; 2196-0216
• DOI: 10.1002/celc.201901801

A series of helquat molecules with increasing number of rings n was studied by electrochemical and break junction methods to provide redox characteristics and single molecule conductance properties. Even though selected species do not contain anchoring groups the molecular junction conductance was observed experimentally and depends strongly on the solvent used. Single molecule conductance G is almost two orders of magnitude higher in water environment compared to mesitylene, whereas the distribution of G values is narrow in water and wide in mesitylene solvent. In the non‐polar environment, G increases with increasing n, contrary to generally accepted notion of decreasing tunneling current with increasing molecular length. This behavior is, however, consistent with electrochemical properties, which showed that longer helquats are reduced more easily than the shorter ones. Furthermore, theoretical computations provided most probable molecular junction configurations of helquats in water solvent with excellent agreement between theoretical and experimental G values. Closing the ring: Helquats represent fast electron‐transfer systems that can be reduced in two one‐ electron steps. Single molecule conductance G of a series of helquats lacking anchoring groups is reported in water and mesitylene solvents. G in water is higher and independent of molecular length, whereas G increases with molecular length in mesitylene and correlates with redox potentials for helquat reduction.