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Cyclophane molecules exhibiting thermally activated delayed fluorescence: linking donor units to influence molecular conformation

DOI: 10.1021/acs.joc.0c02174 DOI Help

Authors: Matthias Hempe (Durham University) , Alastair K. Harrison (Durham University) , Jonathan S. Ward (Durham University) , Andrei S. Batsanov (Durham University) , Mark A. Fox (Durham University) , Fernando B. Dias (Durham University) , Martin R. Bryce (Durham University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: The Journal Of Organic Chemistry

State: Published (Approved)
Published: November 2020
Diamond Proposal Number(s): 22240

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.

Subject Areas: Chemistry, Materials

Instruments: I19-Small Molecule Single Crystal Diffraction

Added On: 29/11/2020 15:04

Discipline Tags:

Chemistry Materials Science Organic Chemistry

Technical Tags:

Diffraction Single Crystal X-ray Diffraction (SXRD)