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Instruments / Technical Area	Publication Details	Published
I19-Small Molecule Single Crystal Diffraction	Achieving conformational control in RTP and TADF emitters by functionalization of the central core Nadzeya A. Kukhta , Rongjuan Huang , Andrei S. Batsanov , Martin R. Bryce , Fernando B. Dias The Journal Of Physical Chemistry C DOI: 10.1021/acs.jpcc.9b08238 Diamond Proposal Number(s): [11145] Show Abstract ▼ Abstract: Three new symmetrical donor–acceptor–donor (D–A–D)-type molecules were prepared with phenothiazine (PTZ) as electron donors and 9,9-dimethylthioxanthene (TX) as the electron acceptor. The PTZ groups are attached at different positions on the acceptor core – ortho or meta to the sulfur of TX. The molecules have been characterized by X-ray crystallography, in-depth photophysical studies and theoretical calculations. This series provides new insights into how molecular functionalization and intramolecular charge transfer determines the singlet-triplet gap ΔEST. Two of the molecules have weak D/A decoupling and a relatively large ΔEST of 0.52 eV which prohibits the upconversion of triplet excitons to the singlet state, showing strong room temperature phosphorescence (RTP). When the TX acceptor strength is enhanced by the attachment of benzoyl substituents a very small ΔEST of <0.01 eV is observed. In this case excitons in the triplet state can be efficiently upconverted to the singlet state via reverse intersystem crossing (RISC) resulting in thermally activated delayed fluorescence (TADF). TADF and RTP are unambiguously assigned by distinctive photophysical data, notably a comparison of degassed and aerated luminescence spectra, temperature-dependent time-resolved fluorescence decays and power dependence of the intensity of delayed emission (for the TADF emitter).	Oct 2019
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
I19-Small Molecule Single Crystal Diffraction	Persistent dimer emission in thermally activated delayed fluorescence materials Marc K. Etherington , Nadzeya A. Kukhta , Heather F. Higginbotham , Andrew Danos , Aisha N. Bismillah , David R. Graves , Paul R. Mcgonigal , Nils Haase , Antonia Morherr , Andrei S. Batsanov , Christof Pflumm , Vandana Bhalla , Martin R. Bryce , Andrew P. Monkman The Journal Of Physical Chemistry C DOI: 10.1021/acs.jpcc.9b01458 Diamond Proposal Number(s): [11145] Show Abstract ▼ Abstract: We expose significant changes in emission color of carbazole-based thermally activated delayed fluorescence (TADF) emitters that arise through the presence of persistent dimer states in thin films and organic light-emitting diodes (OLEDs). Direct photoexcitation of this dimer state in 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN) reveals the significant influence of dimer species on the color purity of its photoluminescence and electrolumines-cence. The dimer species is sensitive to the sample preparation method and its enduring presence contributes to the widely reported concentration-mediated redshift in the photoluminescence and electroluminescence of evaporated thin films. This discovery has significant implications on the usability of these, and similar, molecules for OLEDs and explains disparate electroluminescence spectra presented in the literature for these compounds. The significant dimer-ization-controlled changes observed in the TADF process and photoluminescence efficiency mean that careful consid-eration of dimer states is imperative in the design of future TADF emitters and the interpretation of previously reported studies of carbazole-based TADF materials.	Apr 2019
I19-Small Molecule Single Crystal Diffraction	Importance of chromophore rigidity on the efficiency of blue thermally activated delayed fluorescence emitters Nadzeya A. Kukhta , Andrei S. Batsanov , Martin R. Bryce , Andrew P. Monkman The Journal Of Physical Chemistry C DOI: 10.1021/acs.jpcc.8b10867 Diamond Proposal Number(s): [11145] Show Abstract ▼ Abstract: Four new symmetrical donor–acceptor–donor (D–A–D)-type molecules are reported with diphenylamine (DPA) or 10,11-dihydro-5H-dibenz[b,f]azepine (Az) as electron donors and 9,9-dimethylthioxanthene-S,S-dioxide (TXO2) as the electron acceptor. The donors are attached at different positions on the acceptor core: either para or meta to the sulfone unit. This series provides new insights into the effects of chromophore rigidity/flexibility on the efficiency of thermally activated delayed fluorescence (TADF). The molecules have been characterized by X-ray crystallography, by in-depth photophysical studies, and by theoretical calculations. The clear differences observed in the photophysical properties when using DPA or Az as a donor are shown to originate from different geometries of the donor unit which, in turn, influence the geometry of the nitrogen lone pair and the donating strength of the corresponding fragment. Thus, a para-substituted Az derivative demonstrated blue TADF in polar media, while the compounds with more flexible DPA units did not show delayed fluorescence. To obtain deep-blue emitters, weaker donating units are needed. A more flexible donor unit leads to increased local excited state (donor) LE emission and reduced TADF. However, a certain amount of flexibility has to be present to ensure deep-blue TADF.	Dec 2018
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 J. Mater. Chem. 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	Influence of Bio-Isosteric Replacement on the Formation of Templating Methanol and Acetonitrile Solvates in Lophines Thomas Kitchen , Connor Melvin , Mohd Nadzri Mohd Najib , Andrei Batsanov , Katharina Edkins Crystal Growth & Design DOI: 10.1021/acs.cgd.6b00655 Diamond Proposal Number(s): [8682] Show Abstract ▼ Abstract: Bio-isosteric replacement is a frequently used tool in medicinal chemistry. While the pharmacological activity is not influenced by the exchange of substituents, the solid-state characteristics and formation of different crystal forms may well be altered dramatically, jeopardizing the processability and safety of the drug compound. In this study we investigate a series of triphenylimidazole (TPI) derivatives as model compounds with the bio-isosteric exchange of only one halogen position (F, Cl, Br, I). Crystallization from two industrially used solvents (methanol and acetonitrile) reveals solvate formation of all TPIs, for which the basic hydrogen bonded motif does not change. The three-dimensional packing depends on the size of the substituent and changes from fluoro- to chloro- and bromo-substitution but remains the same for the larger iodo-substituent. From acetonitrile, only F-TPI and Cl-TPI form an isomorphic channel solvate, which in both cases desolvates reversibly to an isomorphic crystal form. Due to the halogen atom lining of the channels, bromine and iodine are too large to generate a stable packing. This study illustrates the importance of understanding the influence of bio-isosteric substitution on the solid state, in order to best utilize this common tool.	Jul 2016
I19-Small Molecule Single Crystal Diffraction	Oligo(aryleneethynylene)s with Terminal Pyridyl Groups: Synthesis and Length Dependence of the Tunneling-to-Hopping Transition of Single-Molecule Conductances Xiaotao Zhao , Cancan Huang , Murat Gulcur , Andrei Batsanov , Masoud Baghernejad , Wenjing Hong , Martin R. Bryce , Thomas Wandlowski Chemistry Of Materials 25 (21), 4340 - 4347 DOI: 10.1021/cm4029484 Diamond Proposal Number(s): [6749] Show Abstract ▼ Abstract: The synthesis is reported of a new series of oligo(aryleneethynylene) (OAE) derivatives of up to ca. 6 nm in molecular length (OAE9) using iterative Pd-mediated Sonogashira cross-coupling methodology. The oligo-p-phenyleneethynylene cores of the molecular wires are functionalized at both termini with pyridyl units for attachment to gold leads. The molecular structures determined by single-crystal X-ray analysis are reported for OAE4, OAE5, OAE7, and OAE8a. The charge transport characteristics of derivatives OAE3–OAE9 in single-molecular junctions have been studied using the mechanically controlled break junction technique. The data demonstrate that the junction conductance decreases with increasing molecular length. A transition from coherent transport via tunneling to a hopping mechanism is found for OAE wires longer than ca. 3 nm.	Nov 2013

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