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31 items found (0 items not approved), displaying 1 to 10.[First/Prev] 1, 2, 3, 4 [Next/Last]

Instruments / Technical Area	Publication Details	Published
I19-Small Molecule Single Crystal Diffraction	Structural analysis of coordination cage/guest complexes prepared with the ‘crystalline sponge’ methodology Christopher G. P. Taylor , James R. Williams , Stephen Argent , Michael D. Ward Crystals 14 DOI: 10.3390/cryst14100873 Diamond Proposal Number(s): [25064, 26668] Open Access Show Abstract ▼ Abstract: The crystalline sponge method has proven invaluable in the preparation and analysis of supramolecular host/guest complexes if the host can be obtained in a suitable crystalline form, allowing the analysis of guest binding modes inside host cavities which can inform other studies into processes such as catalysis. Here, we report the structures of a set of ten host/guest complexes using an octanuclear coordination cage host with a range of small-molecule neutral organic guests including four aromatic aldehydes and ketones, three cyclic lactams, and three epoxides. In all cases, the cavity-bound guests are anchored by a collection of CH•••O hydrogen-bonding interactions between an O atom on the guest and a convergent set of CH protons at a pocket on the cage interior surface. Depending on guest size and the presence of solvent molecules as additional guests, there may be one or two cavity-bound guests, with small aromatic guests forming π-stacked pairs. Some guests (the lactams) participate in additional NH•••F H-bonding interactions with surface-bound fluoroborate anions, which indicate the type of anion/guest interactions thought to be responsible for solution-phase catalytic reactions of bound guests.	Oct 2024
I15-Extreme Conditions	Ligand solid-solution tuning of magnetic and mechanical properties of the van der Waals metal-organic magnet NiCl2 (btd) 1-x (bod)x Emily Myatt , Simrun Lata , Jem Pitcairn , Dominik Daisenberger , Silva M. Kronawitter , Sebastian A. Hallweger , Gregor Kieslich , Stephen P. Argent , Jeremiah P. Tidey , Matthew J. Cliffe Chemical Communications DOI: 10.1039/D4CC04214J Diamond Proposal Number(s): [30815] Open Access Show Abstract ▼ Abstract: Van der Waals (vdW) magnets offer unique opportunities for exploring magnetism in the 2D limit. Metal-organic magnets (MOM) are of particular interest as the functionalisation of organic ligands can control their physical properties. Here, we demonstrate tuning of mechanical and magnetic function of a noncollinear vdW ferromagnet, NiCl2(btd) (btd = 2,1,3-benzothiadiazole), through creating solid-solutions with the oxygen-substituted analogue ligand 2,1,3-benzoxadiazole (bod). We synthesise solid-solutions, NiCl2(btd)1–x(bod)x , up to x = 0.33 above which we find mixtures form, primarily composed of a new 1D coordination polymer NiCl2(bod)2. Magnetometry on this series shows that bod incorporation reduces the coercivity significantly (up to 60%), without significantly altering the ordering temperatures. Our high pressure synchrotron diffraction measurements up to 0.4 GPa demonstrate that the stiffest axis is the b axis, through the Ni-N-(O/S)-N-Ni bonds, and the softest is the interlayer direction. Doping with bod fine-tunes this compressibility, softening the layers, but stiffening the interlayer axis. This demonstrates that substitution of organic ligands in vdW MOMs can be used to realise targetted magnetic and mechanical properties.	Oct 2024
I19-Small Molecule Single Crystal Diffraction	Structural transformations of metal-organic cages through tetrazine-alkene reactivity Martin R. Black , Soumalya Bhattacharyya , Stephen P. Argent , Ben S. Pilgrim Journal Of The American Chemical Society DOI: 10.1021/jacs.4c08591 Diamond Proposal Number(s): [28766, 36069] Open Access Show Abstract ▼ Abstract: The assembly of metal–organic cages is governed by metal ion coordination preferences and the geometries of the typically rigid and planar precursor ligands. PdnL2n cages are among the most structurally diverse, with subtle differences in the metal–ligand coordination vectors resulting in drastically different assemblies, however almost all rely on rigid aromatic linkers to avoid the formation of intractable mixtures. Here we exploit the inverse electron-demand Diels–Alder (IEDDA) reaction between tetrazine linker groups and alkene reagents to trigger structural changes induced by post-assembly modification. The structure of the 1,4-dihydropyridazine produced by IEDDA (often an afterthought in click chemistry) is crucial; its two sp3 centers increase flexibility and nonplanarity, drastically changing the range of accessible coordination vectors. This triggers an initial Pd4L8 tetrahedral cage to transform into different Pd2L4 lantern cages, with both the transformation extent (thermodynamics) and rate (kinetics) dependent on the alkene dienophile selected. With cyclopentene, the unsymmetrical 1,4-dihydropyridazine ligands undergo integrative sorting in the solid state, with both head-to-tail orientation and enantiomer selection, leading to a single isomer from the 39 possible. This preference is rationalized through entropy, symmetry, and hydrogen bonding. Subsequent oxidation of the 1,4-dihydropyridazine to the aromatic pyridazine rigidifies the ligands, restoring planarity. The oxidized ligands no longer fit in the lantern structure, inducing further structural transformations into Pd4L8 tetrahedra and Pd3L6 double-walled triangles. The concept of controllable addition of limited additional flexibility and then its removal through well-defined reactivity we envisage being of great interest for structural transformations of any class of supramolecular architecture.	Sep 2024
I19-Small Molecule Single Crystal Diffraction	Organofunctionalized borotungstate polyoxometalates as tunable photocatalysts for oxidative dimerization of amines Nicole Tsang , Alexander Kibler , Stephen P. Argent , Hon Wai Lam , Kieran D. Jones , Graham N. Newton Chemical Science DOI: 10.1039/D4SC03534H Diamond Proposal Number(s): [28766] Open Access Show Abstract ▼ Abstract: Organofunctionalised borotungstate Keggin polyoxometalates, (nBu4N)3H[HBW11O39(P(O)Ph)2] (PBW11), (nBu4N)3H[HBW11O39(As(O)Ph)2] (AsBW11), and (nBu4N)4[HBW11O39(PhSiOSiPh)] (SiBW11), were synthesized and structurally characterized. Cyclic voltammetry showed that the electronic properties of the clusters are dependent on the nature of the appended main group atoms (P, As, or Si). The first reduction potentials were found to shift positively with respect to that of the unmodified parent species (nBu4N)5[BW12O40], with PBW11 showing the largest shift at +100 mV. All clusters were evaluated as photocatalysts for the oxidative dimerization of amines where the organophosphonate hybrid PBW11 was found to be the most active. This study demonstrates how organofunctionalization of polyoxometalates may be used to tune and improve their performance as photocatalysts for organic reactions.	Aug 2024
I19-Small Molecule Single Crystal Diffraction	Mechanistic investigations of the Fe(II) mediated synthesis of squaraines Yu Liu , Nathan T. Coles , Nathalia Cajiao , Laurence J. Taylor , E. Stephen Davies , Alistair Barbour , Patrick J. Morgan , Kevin Butler , Ben Pointer-Gleadhill , Stephen P. Argent , Jonathan Mcmaster , Michael L. Neidig , David Robinson , Deborah L. Kays Chemical Science DOI: 10.1039/D4SC01286K Diamond Proposal Number(s): [28766] Open Access Show Abstract ▼ Abstract: The scission and homologation of CO is a fundamental process in the Fischer-Tropsch reaction. However, given the heterogeneous nature of the catalyst and forcing reaction conditions, it is difficult to determine the intermediates of this reaction. Here we report detailed mechanistic insight into the scission/homologation of CO by two-coordinate iron terphenyl complexes. Mechanistic investigations, conducted using in situ monitoring and reaction sampling techniques (IR, NMR, EPR and Mössbauer spectroscopy) and structural characterisation of isolable species, identifies a number of proposed intermediates. Crystallographic and IR spectroscopic data reveal a series of migratory insertion reactions from 1Mes to 4Mes. Further studies past the formation of 4Mes suggest that ketene complexes are formed enroute to squaraine 2Mes and iron carboxylate 3Mes, with a number of ketene containing structures being isolated, in addition to the formation of unbound, protonated ketene. The synthetic and mechanistic studies are supported by DFT calculations.	May 2024
I19-Small Molecule Single Crystal Diffraction	Porous isoreticular non-metal organic frameworks Megan O'Shaughnessy , Joseph Glover , Roohollah Hafizi , Mounib Barhi , Rob Clowes , Samantha Y. Chong , Stephen P. Argent , Graeme M. Day , Andrew I. Cooper Nature 341 DOI: 10.1038/s41586-024-07353-9 Open Access Show Abstract ▼ Abstract: Metal–organic frameworks (MOFs) are useful synthetic materials that are built by the programmed assembly of metal nodes and organic linkers. The success of MOFs results from the isoreticular principle, which allows families of structurally analogous frameworks to be built in a predictable way. This relies on directional coordinate covalent bonding to define the framework geometry. However, isoreticular strategies do not translate to other common crystalline solids, such as organic salts, in which the intermolecular ionic bonding is less directional. Here we show that chemical knowledge can be combined with computational crystal-structure prediction6 (CSP) to design porous organic ammonium halide salts that contain no metals. The nodes in these salt frameworks are tightly packed ionic clusters that direct the materials to crystallize in specific ways, as demonstrated by the presence of well-defined spikes of low-energy, low-density isoreticular structures on the predicted lattice energy landscapes. These energy landscapes allow us to select combinations of cations and anions that will form thermodynamically stable, porous salt frameworks with channel sizes, functionalities and geometries that can be predicted a priori. Some of these porous salts adsorb molecular guests such as iodine in quantities that exceed those of most MOFs, and this could be useful for applications such as radio-iodine capture. More generally, the synthesis of these salts is scalable, involving simple acid–base neutralization, and the strategy makes it possible to create a family of non-metal organic frameworks that combine high ionic charge density with permanent porosity.	May 2024
I19-Small Molecule Single Crystal Diffraction	Silver(I)-catalyzed synthesis of cuneanes from cubanes and their investigation as isosteres Elliot Smith , Kieran D. Jones , Luke O’brien , Stephen P. Argent , Christophe Salome , Quentin Lefebvre , Alain Valery , Mina Böcü , Graham N. Newton , Hon Wai Lam Journal Of The American Chemical Society 28 DOI: 10.1021/jacs.3c03207 Diamond Proposal Number(s): [28766] Open Access Show Abstract ▼ Abstract: Bridged or caged polycyclic hydrocarbons have rigid structures that project substituents into precise regions of 3D space, making them attractive as linking groups in materials science and as building blocks for medicinal chemistry. The efficient synthesis of new or underexplored classes of such compounds is, therefore, an important objective. Herein, we describe the silver(I)-catalyzed rearrangement of 1,4-disubstituted cubanes to cuneanes, which are strained hydrocarbons that have not received much attention since they were first described in 1970. The synthesis of 2,6-disubstituted or 1,3-disubstituted cuneanes can be achieved with high regioselectivities, with the regioselectivity being dependent on the electronic character of the cubane substituents. A preliminary assessment of cuneanes as scaffolds for medicinal chemistry suggests cuneanes could serve as isosteric replacements of trans-1,4-disubstituted cyclohexanes and 1,3-disubstituted benzenes. An analogue of the anticancer drug sonidegib was synthesized, in which the 1,2,3-trisubstituted benzene was replaced with a 1,3-disubstituted cuneane.	Jul 2023
I19-Small Molecule Single Crystal Diffraction	Quantitative Raman microscopy to describe structural organisation in hollow microcrystals built from silicon catecholate and amines Victor V. Volkov , Toby J. Blundell , Stephen Argent , Carole C. Perry Dalton Transactions DOI: 10.1039/D3DT00856H Diamond Proposal Number(s): [298766] Open Access Show Abstract ▼ Abstract: Macroscopic scale hollow microcrystals are a promising group of materials for gas and liquid uptake as well as sensing. In this contribution we describe the structure of hollow hexagonal cross-section crystals formulated as salts of a silicon catecholate anion and a tetramethylenediamine (TEMED) cation. Using a combination of X-ray single crystal diffraction, Raman spectroscopy and quantum chemistry we explore the structural properties of the hollow microcrystals. With the X-ray structural data as a starting point and assisted with quantum chemistry we compute Raman tensors to fit polarisation sensitive spectral responses and predict the orientation and packing of unit cells in respect to the long and short axis of the synthesised microcrystals. Using these newly developed methods for predicting molecular Raman responses in space with dependence on local orientation, we present the quantitative analysis of experimental Raman images of both hexagonal and tetragonal cross section hollow microcrystals formed from silicon catecholate anions using different amines as counterions. We describe the distributions of chemical components at the surfaces and edges of microcrystals, address the effect of catcholate hydrophobicity on water uptake and discuss possible strategies in chemical and post-assembly modifications to widen the functional properties of this group of environmentally friendly silicon organic framework (SOF) materials.	May 2023
I19-Small Molecule Single Crystal Diffraction	Highly electron deficient diketopyrrolopyrroles Joshua Humphreys , Ferdinando Malagreca , Paul Hume , E. Stephen Davies , Stephen P. Argent , Tracey D. Bradshaw , David B. Amabilino Chemical Communications DOI: 10.1039/D2CC06770F Open Access Show Abstract ▼ Abstract: The synthesis, spectroelectrochemical and structural characteristics of highly electron-accepting diketopyrrrolopyrrole (DPP) molecules with adjoining pyridinium rings is reported, along with an assessment of their toxicity, which is apparently low. The compounds show reversible electrochemistry and in one subfamily a massive increase in molar extinction coefficient upon electrochemical reduction.	Jan 2023
I19-Small Molecule Single Crystal Diffraction	Reactions of polyaromatic molecules in crystals under electron beam of the transmission electron microscope Kayleigh L. Y. Fung , Benjamin L. Weare , Michael W. Fay , Stephen P. Argent , Andrei N. Khlobystov Micron 7 DOI: 10.1016/j.micron.2022.103395 Show Abstract ▼ Abstract: Reactivity of a series of related molecules under the 80 keV electron beam have been investigated and correlated with their structures and chemical composition. Hydrogenated and halogenated derivatives of hexaazatrinaphthylene, coronene, and phthalocyanine were prepared by sublimation in vacuum to form solventless crystals then deposited onto transmission electron microscopy (TEM) grids. The transformation of the molecules in the microcrystals were triggered by an 80 keV electron beam in the TEM and studied using correlated selected area electron diffraction, conventional bright field imaging, and energy dispersive X-ray spectroscopy. The critical fluence (ē nm-2) required to cause a disappearance of the diffraction pattern was recorded and used as a measure of the reactivity of the molecules. The same electron flux (102 ē nm-2 s-1) was used throughout. Fully halogenated molecules were found to be the most stable and did not change significantly under our experimental conditions, followed by fully hydrogenated molecules with critical fluences of 104 ē nm-2. Surprisingly, semi-halogenated molecules that contained an equal number of hydrogen and halogen atoms were found to be the least stable, with critical fluences an order of magnitude lower at 103 ē nm-2. This is attributed to elimination of H-X (where X = F or Cl), followed by polymerisation of aryne / aryl radicals within the crystal. The critical fluence for the semi-fluorinated hexaazatrinaphthylene is the lowest as the presence of water molecules in its crystal lattice significantly decreased the stability of the organic molecules under the electron beam. Semi-halogenation reduces the beam stability of organic molecules compared to the parent hydrogenated molecule, thus providing the chemical guidance for design of electron beam stable materials. Understanding of molecular reactivity in the electron beam is necessary for advancement of molecular imaging and analysis methods by the TEM, molecular materials processing, and electron beam-driven synthesis of novel materials.	Dec 2022

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