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Distinct Helical Molecular Orbitals Through Conformational Lock

preprint
submitted on 23.04.2020 and posted on 27.04.2020 by Ani Ozcelik, Daniel Aranda Ruiz, Sara Gil-Guerrero, Xaquín A. Pola-Otero, Maria Talavera, Liangxuan Wang, Santosh Kumar Behera, Johannes Gierschner, Ángeles Peña-Gallego, Fabrizio Santoro, Raquel Pereira-Cameselle, José Lorenzo Alonso Gómez
Several theoretical studies have proposed strategies to reach helical molecular orbitals (Hel-MOs) in [n]cumulenes. While chiral even-[n] cumulenes feature Hel-MOs, odd-[n] cumulenes may also present them if the terminal groups lie on different planes. However, the hitherto proposed systems have been either experimentally unfeasible or resulted in opposite pseudo-degenerated Hel-MOs, impeding their use in real applicatons. To overcome this challenge, we hereby demonstrate the introduction of a remarkable energy difference between helical orbitals of opposite twist by fixing the torsion angle between the terminal groups in butadiyne fragments. In order to experimentally lock the conformation of the terminal groups, we designed cyclic architectures by combining acetylenes with chiral spirobifluorenes. A straightforward synthetic strategy along with the high stability allowed the isolation and full characterization of systems presenting distinct helical orbitals. Finally, a thorough computational analysis revealed that the most significant optical responses of these systems originate mainly from the exciton coupling between the featured diphenylbutadiyne fragments. This novel strategy opens now access to the development of systems with distinct helical molecular orbitals suitable for their implementation into chiroptical and optoelectronic applications.

Funding

Xunta de Galicia (ED431F 2016/005 and GRC2019/24), IIS Galicia Sur, and IBEROS (0245_IBEROS_1_E), MINECO-FEDER project CTQ2017-87054

History

Email Address of Submitting Author

lorenzo@uvigo.es

Institution

universidade de Vigo

Country

Spain

ORCID For Submitting Author

0000-0002-6107-0120

Declaration of Conflict of Interest

no conflicts of interest

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