Charge Tunneling along Short Oligoglycine Chains

• Published in: Angewandte Chemie 2015-12, Vol.127 (49), p.14956-14960
• Main Authors: Baghbanzadeh, Mostafa, Bowers, Carleen M., Rappoport, Dmitrij, Żaba, Tomasz, Gonidec, Mathieu, Al-Sayah, Mohammad H., Cyganik, Piotr, Aspuru-Guzik, Alan, Whitesides, George M.
• Format: Article
• Language: English
• Subjects: Alkanes; Amides; Biologische Leitfähigkeit; Charge; Charge transport; Chemistry; Compatibility; Cysteine; Density functional theory; Dichtefunktionaltheorie; Gallium oxides; Methylene; Oligopeptide; Organische Elektronik; Substrates; Superaustausch-Tunneln; Tunneling
• ISSN: 0044-8249; 1521-3757
• DOI: 10.1002/ange.201507271

This work examines charge transport (CT) through self‐assembled monolayers (SAMs) of oligoglycines having an N‐terminal cysteine group that anchors the molecule to a gold substrate, and demonstrate that CT is rapid (relative to SAMs of n‐alkanethiolates). Comparisons of rates of charge transport‐using junctions with the structure AuTS/SAM//Ga2O3/EGaIn (across these SAMs of oligoglycines, and across SAMs of a number of structurally and electronically related molecules) established that rates of charge tunneling along SAMs of oligoglycines are comparable to that along SAMs of oligophenyl groups (of comparable length). The mechanism of tunneling in oligoglycines is compatible with superexchange, and involves interactions among high‐energy occupied orbitals in multiple, consecutive amide bonds, which may by separated by one to three methylene groups. This mechanistic conclusion is supported by density functional theory (DFT). Superaustausch‐Tunneln: Selbstorganisierte Monoschichten (SAMs) aus Oligoglycinen ((Gly)n, n=0–5) haben eine höhere Tunnel‐Leitfähigkeit als SAMs aus Alkanthiolaten, was sich experimentell und theoretisch quantifizieren lässt. Dichtefunktionalrechnungen identifizieren die Details der Orbitale und elektronischen Kopplungen, die am Superaustausch‐Tunneln beteiligt sind.