Materials Chemistry, Short talk
Mat-026

Exploration of Asymmetric Paracyclophanes Functionalized with Azulene and NDI or PMDI

G. Graf1, M. Mukherjee2, E. Zyaee3, C. Negrete-Vergara1, V. Slama2, H. Frey3, T. Feurer3, U. Röthlisberger2*, S. Liu1*
1Department of Chemistry, Biochemistry and Pharmaceutical Sciences, W. Inäbnit Laboratory for Molecular Quantum Materials and WSS-Research Center for Molecular Quantum Systems, University of Bern, Freiestrasse 3, Bern, Switzerland, 2Laboratory of Computational Chemistry and Biochemistry, Institute of Chemical Sciences and Engineering, EPFL, Lausanne, Switzerland, 3Institute of Applied Physics, University of Bern, Sidlerstrasse 5, Bern, Switzerland

Molecular devices such as diodes typically consist of an electron donor (D) and acceptor (A) linked by a bridge. The bridge acts as a separator, ensuring a physical distance between the donor and acceptor units, so that current can only flow in one direction. Upon photoexcitation, an intramolecular charge-transfer (CT) occurs. A good understanding of these CT processes is crucial for developing new molecular devices.1 Paracyclophanes have emerged as attractive scaffolds for molecular devices because their rigid and tunable architectures are well-suited for probing CT interactions.2 In this work, we designed two novel paracyclophanes that contain two parallel π-systems, forming a D-A ensemble (see figure below). The electron donor is composed of azulene (Az), a blue emitter with a large inherent dipole moment.3 On the other hand, naphthalene-tetracarboxylic diimide (NDI) and pyromellitic diimide (PMDI) have both a high electron affinity and can serve as efficient electron acceptors. When combined, they can undergo photoinduced through-space charge transfer (TSCT), resulting in a substantial increase in electric dipole moment. A detailed study of single-crystal structures and redox and optical properties, supported by DFT calculations, showed that the TSCT interactions are strongly affected by the geometry and spatial alignment of D and A units within the paracyclophane framework.

[1] Sascha Ullbrich, Johannes Benduhn, Xiangkun Jia, Vasileios C. Nikolis, Kristofer Tvingstedt, Fortunato Piersimoni, Steffen Roland, Yuan Liu, Jinhan Wu, Axel Fischer, Dieter Neher, Sebastian Reineke, Donato Spoltore, Koen Vandewal, Nature Materials, 2019, 18, 459–464. [2] Z. Wang, Y. Liu, X. Quan, W. Zhang, R. Tan, H. Gu, C. Sheng, C. Duan, P. Xing, J. H. Wan. Angewandte Chemie – International Edition, 2025, 64, e202413295. [3] Hanshen Xin, Bin Hou, Xike Gao, Accounts of Chemical Research, 2021, 54, 1737–1753.