The modular synthesis of a series of nanoscale phenylene bicyclophanes with an intraannular orthogonal pillar is described. The compounds are obtained by a Suzuki cross-coupling condensation and are characterized by mass spectrometry and NMR spectroscopy as well as in situ scanning tunneling microscopy at the solid/liquid interface of highly ordered pyrolytic graphite. In addition, their structures and conformations are supported by quantum chemical calculations, also after adsorption to the substrate. A set of two alkyl chain substitution patterns as well as a combination of both were investigated with respect to their ability to form extended 2D-crystalline superstructures on graphite. It shows that not the most densely packed surface coverage gives the most stable structure, but the largest number of alkyl chains per molecule determines the structural robustness to alterations at the pillar functionality.
Daniel Kalle, Joshua Bahr, Tristan J. Keller, Julius B. Kleine Büning, Stefan Grimme, Markus Bursch,* Stefan-S. Jester,* SigurdHöger*
Chem. Eur. J. 2023, e202302662. doi.org/10.1002/chem.202302662.