Corrole- and Helicene-based functional Molecules studied by DC and AC Scanning Tunnelling Microscopy

In this thesis, functional corrole- and helicene-based molecules were studied by means of low temperature scanning tunneling microscopy (LT-STM), scanning tunneling spectroscopy (STS) and radio frequency scanning tunneling spectroscopy (rf-STS) at the single-molecule scale. Two different systems were investigated. Corrole-like molecules may stabilize various metal ions in high oxidation states, acting as catalysts for H2O splitting and CO2 reduction. Metal-organic complexes are essential in many processes in nature and artifcial applications, like cancer treatment, quantum computing and solar technologies. A versatile test system is one of the most stable free-base corroles, the archetypal H3TpFPC, which has been well studied in the liquid phase, but not when adsorbed on solid surfaces. Adsorption and temperature dependent self-assembly of H3TpFPC, evaporated onto the Ag(111) surface, were studied by high resolution real-space STM images. By identifying single corrole molecules, the distribution of different ring-closed conformers was analyzed and evaluated, to test theoretical predictions. The experiments yielded non-regular structures for H3TpFPC/Ag(111) in the temperature range from 450K to 530K and allowed to attribute single corrole molecules specifcally to certain conformers. Text-book-like examples for mechanical springs in the nanoscopic range, namely helicene molecules, were studied. Adsorption, growth and self-assembly of molecular clusters on Ag(111) were investigated by STM. Based on previous work of our group, the young rf-STS technique was utilized for the detection of driven (mechanical) oscillations of [7]helicene molecules (BA7H) adsorbed on Ag(111). My rf-STS experiments on BA7H yielded resonance-like peaks in the conductance vs. frequency curves, attributable to single BA7H molecules. Local tunneling spectra were recorded to gain information on the electronic structure of BA7H, like molecular orbital energies.submitted by Jeffrey SchusterUniversität Linz, Masterarbeit, 2018(VLID)258195