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Instruments / Technical Area	Publication Details	Published	Actions
I19-Small Molecule Single Crystal Diffraction	Cyclophane molecules exhibiting thermally activated delayed fluorescence: linking donor units to influence molecular conformation Matthias Hempe , Alastair K. Harrison , Jonathan S. Ward , Andrei S. Batsanov , Mark A. Fox , Fernando B. Dias , Martin R. Bryce The Journal Of Organic Chemistry DOI: 10.1021/acs.joc.0c02174 Diamond Proposal Number(s): [22240] Show Abstract ▼ 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.	Nov 2020
I19-Small Molecule Single Crystal Diffraction	The influence of molecular geometry on the efficiency of thermally activated delayed fluorescence Roberto S. Nobuyasu , Jonathan S. Ward , Jamie Gibson , Beth A. Laidlaw , Zhongjie Ren , Przemyslaw Data , Andrei S. Batsanov , Thomas J. Penfold , Martin R. Bryce , Fernando B. Dias Journal Of Materials Chemistry C 7, 6672-6684 DOI: 10.1039/C9TC00720B Diamond Proposal Number(s): [11145] Open Access Show Abstract ▼ Abstract: In this work we successfully developed a strategy for positively influencing the conformation of thermally activated delayed fluorescence (TADF) molecules containing phenothiazine as the electron donor (D) unit, and dibenzothiophene-S,S-dioxide as the acceptor (A), linked in D–A and D–A–D structures. In this strategy the effect of restricted molecular geometry is explored to maximize TADF emission. The presence of bulky substituents in different positions on the donor unit forces the molecules to adopt an axial conformer where the singlet charge transfer state is shifted to higher energy, resulting in the oscillator strength and luminescence efficiency decreasing. With bulky substituents on the acceptor unit, the molecules adopt an equatorial geometry, where the donor and acceptor units are locked in relative near-orthogonal geometry. In this case the individual signatures of the donor and acceptor units are evident in the absorption spectra, demonstrating that the substituent in the acceptor uncouples the electronic linkage between the donor and acceptor more effectively than with donor substitution. In contrast with the axial conformers that show very weak TADF, even with a small singlet triplet gap, molecules with equatorial geometry show stronger oscillator strength and luminescence efficiency and are excellent TADF emitters. Acceptor-substituted molecules 6 and 7 in particular show extremely high TADF efficiency in solution and solid film, even with a singlet–triplet energy gap around 0.2 eV. This extensive study provides important criteria for the design of novel TADF and room temperature phosphorescence (RTP) emitters with optimized geometry.	May 2019

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