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Instruments / Technical Area	Publication Details	Published
I19-Small Molecule Single Crystal Diffraction	Thermodynamic equilibrium between locally excited and charge-transfer states through thermally activated charge transfer in 1-(pyren-2′-yl)-o-carborane Lei Ji , Stefan Riese , Alexander Schmiedel , Marco Holzapfel , Maximillian Fest , Jörn Nitsch , Basile F. E. Curchod , Alexandra Friedrich , Lin Wu , Hamad H. Al Mamari , Sebastian Hammer , Jens Pflaum , Mark A. Fox , David J. Tozer , Maik Finze , Christoph Lambert , Todd B. Marder Chemical Science 492 DOI: 10.1039/D1SC06867A Diamond Proposal Number(s): [18456] Open Access Show Abstract ▼ Abstract: Reversible conversion between excited-states plays an important role in many photophysical phenomena. Using 1-(pyren-2′-yl)-o-carborane as a model, we studied the photoinduced reversible charge-transfer (CT) process and the thermodynamic equilibrium between the locally-excited (LE) state and CT state, by combining steady state, time-resolved, and temperature-dependent fluorescence spectroscopy, fs- and ns-transient absorption, and DFT and LR-TDDFT calculations. Our results show that the energy gaps and energy barriers between the LE, CT, and a non-emissive ‘mixed’ state of 1-(pyren-2′-yl)-o-carborane are very small, and all three excited states are accessible at room temperature. The internal-conversion and reverse internal-conversion between LE and CT states are significantly faster than the radiative decay, and the two states have the same lifetimes and are in thermodynamic equilibrium.	Apr 2022
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	Bright green PhOLEDs using cyclometalated diiridium(iii) complexes with bridging oxamidato ligands as phosphorescent dopants Ahmed M’hamedi , Mark A. Fox , Andrei S. Batsanov , Hameed A. Al-Attar , Andrew P. Monkman , Martin R. Bryce Journal Of Materials Chemistry C 5, 6777-6789 DOI: 10.1039/C7TC00628D Diamond Proposal Number(s): [11145] Open Access Show Abstract ▼ Abstract: In contrast to monoiridium complexes, the study of diiridium complexes as dopants in phosphorescent organic light-emitting devices (PhOLEDs) is largely unexplored. We now describe the syntheses, detailed NMR analyses, X-ray crystal structures and optoelectronic properties of the new cyclometalated diiridium complexes 5 and 6 in which the iridium centres are bridged by oxamidato ligands. These complexes contain diastereomers – the meso form (ΔΛ) and the racemic form consisting of two enantiomers (ΔΔ and ΛΛ) – with anti-oxamidato bridges. The precursor μ-dichloro-bridged complex 4 is very weakly emissive in solution, whereas the oxamidato bridged complexes 5 and 6 are highly emissive (ΦPL 73% and 63%) with short excited state lifetimes of τP 0.84 and 1.16 μs, respectively. Cyclic voltammetry studies demonstrate that the oxamidato bridging ligand plays a role in mediating intramolecular interactions between the iridium centres. Density functional theory (DFT) calculations and time dependent-DFT (TD-DFT) calculations provide further insights into the structural, electronic, and photophysical properties of the complexes in their ground and excited states. Phosphorescent organic light-emitting diodes (PhOLEDs) using complexes 5 and 6 as the emissive dopants in a simple architecture using a solution-processed active layer give bright green electroluminescence with remarkably high luminance (Lmax > 25[thin space (1/6-em)]000 cd m−2) for diiridium complexes.	Jun 2017
I19-Small Molecule Single Crystal Diffraction	Syntheses and structures of buta-1,3-diynyl complexes from "on complex" cross-coupling reactions Marie-Christine Oerthel , Dmitry Yufit , Mark A. Fox , Martin R. Bryce , Paul J. Low Organometallics 34 (11), 2395 - 2405 DOI: 10.1021/om501186c Diamond Proposal Number(s): [6749] Show Abstract ▼ Abstract: The Pd(PPh3)4/CuI-cocatalyzed reaction of Ru(CñMCCñMCH)(PPh3)2Cp (2) with aryl iodides, Ar-I (3, Ar = C6H4CN-4 (a); C6H4Me-4 (b); C6H4OMe-4 (c); 2,3- dihydrobenzo[b]thiophene (d); C5H4N (e)) proceeds smoothly in diisopropylamine and under an inert atmosphere to give the substituted buta-1,3-diynyl complexes Ru(CñM CCñMCAr)(PPh3)2Cp (4a-e) in moderate to good yield. The procedure allows the rapid preparation of a range of metal complexes of arylbuta-1,3-diynyl ligands without necessitating the prior synthesis of the individual buta-1,3-diynes as ligand precursors. Similar reaction of 2 with half an equivalent of 1,4- diiodobenzene affords the bimetallic derivative {Ru- (PPh3)2Cp}2(Ê-CñMCCñMC-1,4-C6H4−CñMCCñMC) (5). In the presence of atmospheric oxygen, homocoupling of the diynyl reagent 2 takes place to provide the octa-1,3,5,7-tetrayndiyl complex {Ru(PPh3)2Cp}2(Ê-CñMCCñMCCñMCCñMC) (6). Crystallographically determined molecular structures are reported for five complexes (4a, 4b, 4d, 5, and 6). Quantum chemical calculations indicate that the HOMOs are mainly located on the C4−C6H4−C4 and C8 bridges for 5 and 6, respectively, while spectroelectrochemical (UV−vis−NIR and IR) studies on 6 establish that oxidation takes place at the C8 bridge, likely followed by cyclodimerization reactions of the bridging ligand.	Jun 2015

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