Cyclophane Molecules Exhibiting Thermally Activated Delayed Fluorescence: Linking Donor Units to Influence Molecular Conformation

Hempe, Matthias; Harrison, Alastair K.; Ward, Jonathan S.; Batsanov, Andrei S.; Fox, Mark A.; Dias, Fernando B.; Bryce, Martin R.

Abstract

The synthetic methodology to covalently link donors to form cyclophane-based thermally activated delayed fluorescence (TADF) molecules is presented. These are the first reported examples of TADF cyclophanes with “electronically innocent” bridges between the donor units. Using a phenothiazine-dibenzothiophene-S,S-dioxide donor–acceptor–donor (D–A–D) system, the two phenothiazine (PTZ) donor units were linked by three different strategies: (i) ester condensation, (ii) ether synthesis, and (iii) ring closing metathesis. Detailed X-ray crystallographic, photophysical and computational analyses show that the cyclophane molecular architecture alters the conformational distribution of the PTZ units, while retaining a certain degree of rotational freedom of the intersegmental D–A axes that is crucial for efficient TADF. Despite their different structures, the cyclophanes and their nonbridged precursors have similar photophysical properties since they emit through similar excited states resulting from the presence of the equatorial conformation of their PTZ donor segments. In particular, the axial–axial conformations, known to be detrimental to the TADF process, are suppressed by linking the PTZ units to form a cyclophane. The work establishes a versatile linking strategy that could be used in further functionalization while retaining the excellent photophysical properties of the parent D–A–D system.

Citation

Hempe, M., Harrison, A. K., Ward, J. S., Batsanov, A. S., Fox, M. A., Dias, F. B., & Bryce, M. R. (2021). Cyclophane Molecules Exhibiting Thermally Activated Delayed Fluorescence: Linking Donor Units to Influence Molecular Conformation. Journal of Organic Chemistry, 86(1), 429-445. https://doi.org/10.1021/acs.joc.0c02174

• Journal Article Type: Article
• Online Publication Date: Nov 28, 2020
• Publication Date: 2021-01
• Deposit Date: Jun 3, 2021
• Publicly Available Date: Nov 28, 2021
• Journal: Journal of Organic Chemistry
• Print ISSN: 0022-3263
• Electronic ISSN: 1520-6904
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 86
• Issue: 1
• Pages: 429-445
• DOI: https://doi.org/10.1021/acs.joc.0c02174
• Public URL: https://durham-repository.worktribe.com/output/1247471