In the Rickhaus lab, there is a strong focus on curved aromatic systems, in particular, saddle shaped molecules, such as carpyridines. We have recently shown that these self-assemble into 2D sheets^1,2, or fibers³, through shape assisted self-assembly. Their intrinsic curvature results in the formation of four disconnected π systems – two pyridine and two carbazole units. This disconnection can be bridged by the insertion of a metal into the carpyridine centre, enabling communication between all four. This has been detected using UV/vis spectroscopy, showing a clear redshift of up to 100 nm upon insertion of Cu, Zn and Co, in addition to quenching of fluorescence (Figure 1, left).  Appending donor and acceptor groups to, for example, the two opposing pyridine units, allows us to probe direct communication through the metal centre, unlocking potential light harvesting properties. This can also be envisaged between both carbazole units too, or even across a corner, carbazole to pyridine.

Forming both linear and cyclic oligomers of these systems also allows us to probe direct metal-metal communication, due to the absence of local aromaticity within each carpyridine monomer. This presents the unique opportunity to investigate electric currents on the molecular level that are forced to pass directly through one or more metal centres. This is of fundamental interest, and also could lead to exciting applications in nanotechnology and microelectronics.

Acknowledgements

We gratefully acknowledge the funding of the Swiss National Science Foundation.

[1] J. F. Woods, L. Gallego, P. Pfister, M. Maaloum, A. Vargas Jentzsch, M. Rickhaus, Nat. Commun. 2022, 13, 3681

[2] J.F. Woods, L. Gallego, A. Maisch, D. Renggli, C. Cuocci, O. Blacque, G. Steinfeld, A. Kaech, B. Spingler, A.V Jentzsch, M. Rickhaus, Nat. Commun. 2023, 14, 4725

[3]  L. Gallego, J.F Woods, R. Butti, P. Szwedziak, A.V. Jentszch, M. Rickhaus Angew. Chem. Int. Ed. 2024, 63, e202318879