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Endohedral Hydrogen Bonding Templates the Formation of a Highly Strained Covalent Organic Cage Compound

preprint
submitted on 09.12.2020, 15:10 and posted on 10.12.2020, 07:35 by Natalie Schäfer, Michael Bühler, Lisa Heyer, Merle Röhr, Florian Beuerle
A highly strained covalent organic cage compound was synthesized from hexahydroxy tribenzotriquinacene (TBTQ) and a meta-terphenyl-based diboronic acid with an additional benzoic acid substituent in 2’-position. Usually, a 120° bite angle in the unsubstituted ditopic linker favors the formation of a [4+6] cage assembly. Here we show that introduction of the benzoic acid group leads to a perfectly preorganized circular hydrogen-bonding array in the cavity of a trigonal-bipyramidal [2+3] cage, which energetically overcompensates the additional strain energy caused by the larger mismatch in bite angles for the smaller assembly. The strained cage compound was analyzed by mass spectrometry and 1H, 13C and DOSY NMR spectroscopy. DFT calculations revealed the energetic contribution of the hydrogen-bonding template to the cage stability. Furthermore, molecular dynamics simulations on early intermediates indicate an additional kinetic effect, as hydrogen-bonding also preorganizes and rigidifies small oligomers to facilitate the exclusive formation of smaller and more strained macrocycles and cages.

Funding

Deutsche Forschungsgemeinschaft (BE4808/2-1)

Klaus Tschira Stiftung gGmbH (GSO/KT 21)

History

Email Address of Submitting Author

florian.beuerle@uni-wuerzburg.de

Institution

University of Würzburg

Country

Germany

ORCID For Submitting Author

0000-0001-7239-8327

Declaration of Conflict of Interest

There are no conflicts to declare.

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