cAAC‐Stabilized 9,10‐diboraanthracenes—Acenes with Open‐Shell Singlet Biradical Ground States

Narrow HOMO–LUMO gaps and high charge‐carrier mobilities make larger acenes potentially high‐efficient materials for organic electronic applications. The performance of such molecules was shown to significantly increase with increasing number of fused benzene rings. Bulk quantities, however, can onl...

Full description

Saved in:
Bibliographic Details
Published in:Angewandte Chemie International Edition 2020-10, Vol.59 (43), p.19338-19343
Main Authors: Saalfrank, Christian, Fantuzzi, Felipe, Kupfer, Thomas, Ritschel, Benedikt, Hammond, Kai, Krummenacher, Ivo, Bertermann, Rüdiger, Wirthensohn, Raphael, Finze, Maik, Schmid, Paul, Engel, Volker, Engels, Bernd, Braunschweig, Holger
Format: Article
Language:English
Subjects:
acenes
Anthracene
Benzene
biradicals
bond Activation
Boron
Carbenes
Current carriers
Elongation
Ground state
heterocycles
Molecular orbitals
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Narrow HOMO–LUMO gaps and high charge‐carrier mobilities make larger acenes potentially high‐efficient materials for organic electronic applications. The performance of such molecules was shown to significantly increase with increasing number of fused benzene rings. Bulk quantities, however, can only be obtained reliably for acenes up to heptacene. Theoretically, (oligo)acenes and (poly)acenes are predicted to have open‐shell singlet biradical and polyradical ground states, respectively, for which experimental evidence is still scarce. We have now been able to dramatically lower the HOMO–LUMO gap of acenes without the necessity of unfavorable elongation of their conjugated π system, by incorporating two boron atoms into the anthracene skeleton. Stabilizing the boron centers with cyclic (alkyl)(amino)carbenes gives neutral 9,10‐diboraanthracenes, which are shown to feature disjointed, open‐shell singlet biradical ground states. 9,10‐diboraanthracenes (DBAs) stabilized by cyclic (alkyl)(amino)carbenes (cAACs) are prepared. EPR spectroscopy and quantum chemistry established disjointed singlet biradical ground states for these molecules, which provides experimental evidence for the predicted open‐shell configurations of larger acenes. The incorporation of two boron atoms is a suitable way to lower the HOMO–LUMO band gaps of acene‐type species.
ISSN:1433-7851
1521-3773
DOI:10.1002/anie.202008206