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17 items found (0 items not approved), displaying 1 to 10.[First/Prev] 1, 2 [Next/Last]

Instruments / Technical Area	Publication Details	Published
I19-Small Molecule Single Crystal Diffraction	Rigidly linked dinuclear platinum(ii) complexes showing intense, excimer-like, near-infrared luminescence Piotr Pander , Melissa T. Walden , Rebecca J. Salthouse , Amit Sil , Dmitry S. Yufit , Fernando B. Dias , J. A. Gareth Williams Journal Of Materials Chemistry C 29 DOI: 10.1039/D3TC03432A Diamond Proposal Number(s): [16177] Open Access Show Abstract ▼ Abstract: Many luminescent platinum(II) complexes undergo face-to-face interactions between neighbouring molecules, leading to bimolecular excited states that may emit at lower energy (dimers and/or excimers). Detailed photophysical studies are reported on dinuclear complexes, in which two NCN-coordinated Pt(II) units are covalently linked by a xanthene such that intramolecular formation of such dimeric or excimeric states is possible. These complexes display strong excimer-like photoluminescence at low concentrations where their monometallic analogues do not. However, a striking difference emerges between complexes where the Pt(NCN) units are directly connected to the xanthene through the tridentate ligand (denoted Class a) and a new class of compounds reported here (Class b) in which the attachment is through a monodentate acetylide ligand. The former require a substantial geometrical rearrangement to move the metal centres of the Pt(NCN) units to a distance short enough to form excimer-like states. The latter require only a small deformation. Consequently, Class a compounds display negligible excimer-like emission in solid films, as the rigid environment hinders the requisite geometric rearrangement. Class b complexes, in contrast, display strong excimer-like emission in film, even at very low loadings. The new dinuclear molecular architecture may thus offer new opportunities in the quest for efficient NIR-emitting devices.	Oct 2023
I19-Small Molecule Single Crystal Diffraction	Pathway complexity in fibre assembly: from liquid crystals to hyper-helical gelmorphs Rafael Contreras-Montoya , James P. Smith , Stephen Boothroyd , Juan A. Aguilar , Marzieh Mirzamani , Martin A. Screen , Dmitry S. Yufit , Mark Robertson , Lilin He , Shuo Qian , Harshita Kumari , Jonathan W. Steed Chemical Science 46 DOI: 10.1039/D3SC03841F Diamond Proposal Number(s): [22240] Open Access Show Abstract ▼ Abstract: Pathway complexity results in unique materials from the same components according to the assembly conditions. Here a chiral acyl-semicarbazide gelator forms three different gels of contrasting fibre morphology (termed ‘gelmorphs’) as well as lyotropic liquid crystalline droplets depending on the assembly pathway. The gels have morphologies that are either hyperhelical (HH-Gel), tape-fibre (TF-Gel) or thin fibril derived from the liquid crystalline phase (LC-Gels) and exhibit very different rheological properties. The gelator exists as three slowly interconverting conformers in solution. All three gels are comprised of an unsymmetrical, intramolecular hydrogen bonded conformer. The kinetics show that formation of the remarkable HH-Gel is cooperative and is postulated to involve association of the growing fibril with a non-gelling conformer. This single molecule dynamic conformational library shows how very different materials with different morphology and hence very contrasting materials properties can arise from pathway complexity as a result of emergent interactions during the assembly process.	Sep 2023
I19-Small Molecule Single Crystal Diffraction	Designer gelators for the crystallization of a salt active pharmaceutical ingredient - mexiletine hydrochloride Jessica L. Andrews , Stuart R. Kennedy , Dmitry S. Yufit , James F. Mccabe , Jonathan W. Steed Crystal Growth & Design 14 DOI: 10.1021/acs.cgd.2c00925 Diamond Proposal Number(s): [22240] Open Access Show Abstract ▼ Abstract: We report an approach to obtain drug-mimetic supramolecular gelators, which are capable of stabilizing metastable polymorphs of the pharmaceutical salt mexiletine hydrochloride, a highly polymorphic antiarrhythmic drug. Solution-phase screening led to the discovery of two new solvated solid forms of mexiletine, a type C 1,2,4-trichlorobenzene tetarto-solvate and a type D nitrobenzene solvate. Various metastable forms were crystallized within the gels under conditions which would not have been possible in solution. Despite typically crystallizing concomitantly with form 1, a pure sample of form 3 was crystallized within a gel of ethyl methyl ketone. Various type A channel solvates were crystallized from gels of toluene and ethyl acetate, in which the contents of the channels varied from those of solution-phase forms. Most strikingly, the high-temperature-stable form 2 was crystallized from a gel in 1,2-dibromoethane: the only known route to access this form at room temperature. These results exemplify the powerful stabilizing effect of drug-mimetic supramolecular gels, which can be exploited in pharmaceutical polymorph screens to access highly metastable or difficult-to-nucleate solid forms.	Oct 2022
I19-Small Molecule Single Crystal Diffraction	Derisking the polymorph landscape: The complex polymorphism of mexiletine hydrochloride Jessica L. Andrews , Sten O. Nilsson Lill , Stefanie Freitag-Pohl , David C. Apperley , Dmitry Yufit , Andrei S. Batsanov , Matthew T. Mulvee , Katharina Edkins , James F. Mccabe , David J. Berry , Michael R. Probert , Jonathan W. Steed Crystal Growth & Design 3 DOI: 10.1021/acs.cgd.1c01009 Diamond Proposal Number(s): [11145] Show Abstract ▼ Abstract: This work presents an updated solid-form discovery approach to the polymorphism of the antiarrhythmic drug mexiletine hydrochloride, in which experimental and computational techniques are combined to provide a rigorous characterization of the solid-form landscape of this compound. The resulting solid forms were characterized by powder and single-crystal X-ray diffraction, IR spectroscopy, differential scanning calorimetry, and 13C solid-state NMR. This approach reveals five solid-form types of mexiletine hydrochloride. Forms 1, 2, and 3 are mutually enantiotropically related anhydrous polymorphs, with Form 1 the room temperature stable form, Form 2 the high-temperature form, and Form 3 the thermodynamically stable polymorph between 148 and 167 °C. The final two forms termed Types A and B comprise two large families of isomorphous channel solvates, including a fourth nonsolvated form isostructural to the Type A solvates. We report 11 modifications of each solvate, in which a diverse range of solvents are included in the channels, without changing the fundamental structure of the drug framework. These experimental results go hand-in-hand with computational crystal structure prediction (using the AstraZeneca crystal structure prediction approach), which together suggest that it is unlikely further nonsolvated forms, at least with Z′ = 1, will be discovered under ambient conditions.	Oct 2021
I19-Small Molecule Single Crystal Diffraction	Alkali metal salts of 10,12-pentacosadiynoic acid and their dosimetry applications Amy V. Hall , Osama M. Musa , David K. Hood , David C. Apperley , Dmitry Yufit , Jonathan W. Steed Crystal Growth & Design 21, 2416-2422 DOI: 10.1021/acs.cgd.1c00031 Diamond Proposal Number(s): [22240] Open Access Show Abstract ▼ Abstract: Wide-dose-range 2D radiochromic films for radiotherapy, such as GAFchromic EBT, are based on the lithium salt of 10,12-pentacosadiynoic acid (Li-PCDA) as the photosensitive component. We show that there are two solid forms of Li-PCDA—a monohydrated form A and an anhydrous form B. The form used in commercial GAFchromic films is form A due to its short needle-shaped crystals, which provide favorable coating properties. Form B provides an enhanced photoresponse compared to that of form A, but adopts a long needle crystal morphology, which is difficult to process. The two forms were characterized by powder X-ray diffraction, Fourier transform infrared spectroscopy, CP-MAS 13C solid-state NMR spectroscopy, and thermogravimetric analysis. In sum, these data suggest a chelating bridging bidentate coordination mode for the lithium ions. The sodium salt of PCDA (Na-PCDA) is also reported, which is an ionic cocrystal with a formula of Na+PCDA–·3PCDA. The PCDA and PCDA– ligands display monodentate and bridging bidentate coordination to the sodium ion in contrast to the coordination sphere of the Li-PCDA forms. In contrast to its lithium analogues, Na-PCDA is photostable.	Mar 2021
I19-Small Molecule Single Crystal Diffraction	The crystal engineering of radiation-sensitive diacetylene cocrystals and salts Amy V. Hall , Dmitry S. Yufit , David C. Apperley , Larry Senak , Osama M. Musa , David K. Hood , Jonathan W. Steed Chemical Science 2 DOI: 10.1039/D0SC02540B Diamond Proposal Number(s): [16117, 222240] Open Access Show Abstract ▼ Abstract: In this work we develop photoreactive cocrystals/salts of a commercially-important diacetylene, 10,12-pentacosadiynoic acid (PCDA, 1) and report the first X-ray crystal structures of PCDA based systems. The topochemical reactivity of the system is modified depending on the coformer used and correlates with the structural parameters. Crystallisation of 1 with 4,4′-azopyridine (2), 4,4′-bipyridyl (3), and trans-1,2-bis(4-pyridyl)ethylene (4) results in unreactive 2[thin space (1/6-em)]:[thin space (1/6-em)]1 cocrystals or a salt in the case of 4,4′-bipiperidine (5). However, salt formation with morpholine (6), diethylamine (7), and n-butylamine (8), results in highly photoreactive salts 12·7 and 1·8 whose reactivity can be explained using topochemical criteria. The salt 1·6 is also highly photoreactive and is compared to a model morpholinium butanoate salt. Resonance Raman spectroscopy reveals structural details of the photopolymer including its conformational disorder in comparison to less photoactive alkali metal salts and the extent of solid state conversion can be monitored by CP-MAS NMR spectroscopy. We also report an unusual catalysis in which amine evaporation from photopolymerised PCDA ammonium salts effectively acts as a catalyst for polymerisation of PCDA itself. The new photoreactive salts exhibit more reactivity but decreased conjugation compared to the commercial lithium salt and are of considerable practical potential in terms of tunable colours and greater range in UV, X-ray, and γ-ray dosimetry applications.	Jul 2020
I19-Small Molecule Single Crystal Diffraction	Tailored supramolecular gel and microemulsion crystallization strategies – is isoniazid really monomorphic? Stuart R. Kennedy , Christopher D. Jones , Dmitry S. Yufit , Catherine E. Nicholson , Sharon J. Cooper , Jonathan W. Steed Crystengcomm vol. 2 DOI: 10.1039/C8CE00066B Diamond Proposal Number(s): [8682] Show Abstract ▼ Abstract: We report the application of supramolecular gel and microemulsion droplet crystallisation methodologies to isoniazid crystallization. Tailored gelators have been designed with isoniazid mimetic functionality in an attempt to control crystal morphology and polymorphic behaviour. Microemulsion crystallisation was investigated to achieve thermodynamic control over drug crystallisation. Both techniques resulted in only a single form of isoniazid implying that it is genuinely monomorphic.	Feb 2018
I19-Small Molecule Single Crystal Diffraction	Gelation by histidine-derived ureas Heather M. Coubrough , Christopher D. Jones , Dmitry Yufit , Jonathan W. Steed Supramolecular Chemistry 30, 384 - 394 DOI: 10.1080/10610278.2017.1376062 Diamond Proposal Number(s): [11145] Show Abstract ▼ Abstract: A series of l-histidine-derived monoureas are described which exhibit versatile organogelation peroperties when the substituent directly attached to the urea is an aliphatic group. Arylureas exhibit a tendency to bind chloride anion.	Feb 2018
I19-Small Molecule Single Crystal Diffraction	Phosphate-free inhibition of calcium carbonate dishwasher deposits Yuexian Hong , Nathalie Letzelter , John S. O. Evans , Dmitry S. Yufit , Jonathan W. Steed Crystal Growth & Design DOI: 10.1021/acs.cgd.7b01508 Diamond Proposal Number(s): [8682] Show Abstract ▼ Abstract: This paper reports the characterization of the composition and morphology of mineral formation on glass and plastic (polymethylmethacrylate) substrates in a dishwasher environment and the identification of suitable phosphate-free mineral crystallization inhibitors as environmentally benign candidates to replace the currently used phosphate-containing inhibitor 1-hydroxyethane 1,1-diphosphoric acid (HEDP). Screening of the calcium carbonate crystallization inhibition performance of twenty-eight different compounds resulted in the identification of two phosphate-free, cyclic polycarboxylic acid inhibitors, which were found in combination to be effective replacements. Each inhibitor proved to be highly substrate specific with all-cis-cyclohexane-1,2,3,4,5,6-hexacarboxylic acid (CHHCA) preventing deposition on glass (where calcite is the dominant polymorph) and cis,cis,cis,cis-cyclopentane-1,2,3,4-tetracarboxylic acid (CPTCA) inhibiting aragonite deposition on polymethylmethacrylate (PMMA). When used in combination, these two species prevented all forms of calcium carbonate deposition on both substrate types. The underlying inhibition mechanism and structural requirements of an efficient calcium carbonate inhibitor are also discussed.	Jan 2018
I19-Small Molecule Single Crystal Diffraction	Scrolling of supramolecular lamellae in the hierarchical self-assembly of fibrous gels Christopher D. Jones , Stuart R. Kennedy , Martin Walker , Dmitry S. Yufit , Jonathan W. Steed Chem 3, 603 - 628 DOI: 10.1016/j.chempr.2017.09.001 Diamond Proposal Number(s): [8682] Show Abstract ▼ Abstract: Lamellar supramolecular assemblies are a common feature of fibrous gels formed by molecules such as peptides and ureas. Competition between gelation and crystallization is highly solvent dependent and can be governed by the dynamics of nascent lamellae in solution. We hypothesize that gel fibrils are formed when the scrolling of lamellae outpaces multilayer stacking. Crystallographic data on model picolyl bis(urea)s were correlated with their gelation properties. Most structures are lamellar, and gels involving fibrous aggregates form concomitantly alongside crystalline solvates. A distinguishing feature of these solvate crystals is that the lamellae have unequal numbers of picolyl groups on opposite faces. Atomistic molecular dynamics simulations show that this asymmetry causes isolated lamellae to scroll spontaneously into fibrils, whereas symmetrical lamellae adopt flat, crumpled, or saddle-like morphologies. Scrolling represents a general mechanism for gel formation, affording networks of unbranched fibers with monodisperse diameters dictated by the equilibrium curvature of the folding lamellae.	Oct 2017

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