Berlin 2018 – wissenschaftliches Programm
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. Rabe1 — 1Department 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 . 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.
 M. Iyoda and H. Shimizu. Chem. Soc. Rev., 44(18): 6411-6424, 2015