Berlin 2018 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 105: Nanostructures at surfaces: 1D and 2D structures and networks III

O 105.1: Vortrag

Donnerstag, 15. März 2018, 17:15–17:30, MA 141

Electrochemical switching of π-expanded macrocycles observed by STM/STS — •Jose D. Cojal Gonzalez1, Masahiko Iyoda2, and Jürgen P. Rabe11Department of Physics & IRIS Adlershof, Humboldt-Universität zu Berlin, Berlin — 2Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Hachioji, Tokyo

Macrocyclic oligothiophenes and their π-extended derivatives have attracted attention for their potential applications in molecular electronics and as components in molecular devices [1]. Here we investigated self-assembled monolayers of four π-expanded oligothiophene macrocycles 8-mers at the interface between their octanoic acid solutions and highly oriented pyrolytic graphite (HOPG). STM height images showed hexagonal ordered 2D-networks with a small difference in unit cells. I–V characteristics confirmed the donor like character of the macrocycles, whose HOMO and LUMO position were consistent with TD-DFT calculations. Moreover, optical gaps determined from UV-Vis absorption and TD-DFT resulted in accordance with the effective gap measured by STS. Cyclic STS measurements showed the switching from the diastereomer Z,Z-8-mer to the E,E-8-mer form after formation of a most stable cationic species, which confirms voltammetry and chemical oxidation experiments. To the best of our knowledge, this result represents the first electrochemical switching experiment under standard STM conditions.

[1] M. Iyoda and H. Shimizu. Chem. Soc. Rev., 44(18): 6411-6424, 2015

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