I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[34893]
Open Access
Abstract: The self-assembly of polyoxometalate (POM) clusters remains challenging because they heavily depend on highly sensitive synthetic conditions that produce a vast library of potential building blocks and subunits such that explicit control is hard. This work reports new strategies to construct compressed molybdenum blue (MB) type cluster rings with a new range of giant MB POM clusters {Mo54}, {Mo58}, {Mo85}, and {Mo108}. These MB clusters prove the limits of the ring structure archetype, showing that it is possible to compress the ring by 100 metal atoms from 154 to 54 yet keep the electronic structure and ring shape. These structures comprise distorted pentagonal building blocks. The compression of the ring is achieved by using a {Mo3S} unit and {Mo5} bridging units. The {Mo85} and {Mo108} clusters exhibit a unique closed architecture, and redox studies demonstrate the reduced nature of these clusters.
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Mar 2025
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B18-Core EXAFS
B22-Multimode InfraRed imaging And Microspectroscopy
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Wanpeng
Lu
,
Claudia E.
Tait
,
Gokay
Avci
,
Xian'E
Li
,
Agamemnon E.
Crumpton
,
Paul
Shao
,
Catherine M.
Aitchison
,
Fabien
Ceugniet
,
Yuyun
Yao
,
Mark D.
Frogley
,
Donato
Decarolis
,
Nan
Yao
,
Kim E.
Jelfs
,
Iain
Mcculloch
Open Access
Abstract: With the pressing urgency to reduce carbon footprint, photocatalytic carbon dioxide reduction has attracted growing attention as a sustainable mitigating option. Considering the important role of catalytic active sites (CASs) in the catalytic processes, control and design of the density and environment of CASs could enhance the catalyst performance. Herein, we report a novel metal–covalent organic framework (MCOF), MCOF-Co-315, featuring earth-abundant Co cocatalysts and conjugation through a covalently bonded backbone. MCOF-Co-315 showed a CO production rate of 1616 μmol g–1 h–1 utilizing Ru(bpy)3Cl2 as photosensitizer and triethanolamine (TEOA) as sacrificial electron donor with a 1.5 AM filter, vis mirror module (390–740 nm), and irradiation intensity adjusted to 1 sun and an especially outstanding apparent quantum yield (AQY) of 9.13% at 450 nm. The photocatalytic reaction was studied with electron paramagnetic resonance (EPR) spectroscopy, X-ray absorption near-edge structure (XANES), and in situ synchrotron Fourier Transform Infrared (FT-IR) spectroscopy, and an underlying mechanism is proposed.
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Mar 2025
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[34573]
Abstract: Lithium argyrodites Li6PS5X (X = Cl, Br, I) are a promising class of solid-state electrolytes with the potential to achieve high conductivities (>10 mS·cm–1) necessary for use in solid-state batteries. Previous research has shown that structural factors, in particular, site disorder between the sulfide and halide anions, can impact the ionic conductivity of lithium argyrodites. One current hypothesis for this correlation between anion site disorder and ionic transport is a connection to the lithium-ion substructure. However, as there is limited research surrounding the anion disordering process itself, this relationship has yet to be fully understood. This research explores the impact of the composition and synthesis on the anion disordering process through the Li6+xP1–xSixS5Br (x = 0 to 0.4 in 0.1 steps) series of substitutions quenched from different annealing temperatures. Ex situ and in situ diffraction studies show that the anion site disorder within the compounds increases upon Si introduction only for samples quenched from higher annealing temperatures but remains relatively constant at lower annealing temperatures. Based on in situ diffraction measurements, we further monitor the effects of anion mobility at elevated temperatures allowing inference of slower anion disordering kinetics with changing compositional content. We complement the experimental work using nudged-elastic band calculations showing the overall preference of anions for their specific sites and the possibility of anion mobility. This work provides insight into the argyrodites and shows that the anion disordering can be monitored and that the composition has strong influences on the disordering process.
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Mar 2025
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[32893]
Open Access
Abstract: The interplay between crystallographic symmetry, structural distortions, and the tolerance factor derived from the isotropic ionic radii of the constituent cations and anions of inorganic perovskites and related materials is a ubiquitous concept in solid-state and materials chemistry. Here we demonstrate a model for the phase transition temperatures associated with these structural distortions in layered perovskites by considering the anisotropy associated with cations, which are susceptible to first-order Jahn–Teller distortions. These symmetry-lowering phase transitions are known to have a significant interplay with superconductivity in the high-TC layered cuprates, and untangling the chemistry that can effectively control them is of the utmost relevance in the search for similar phenomena in the nickelates, the study of which has been greatly stimulated by recent reports of high-pressure superconductivity.
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Feb 2025
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I03-Macromolecular Crystallography
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Gijs
Ruijgrok
,
Wendy A.
Offen
,
Isabelle B.
Pickles
,
Deepa
Raju
,
Thanasis
Patsos
,
Casper
De Boer
,
Tim
Ofman
,
Joep
Rompa
,
Daan
Van Oord
,
Eleanor J.
Dodson
,
Alexander
Beekers
,
Thijs
Voskuilen
,
Michela
Ferrari
,
Liang
Wu
,
Antonius P. A.
Janssen
,
Jeroen D. C.
Codée
,
P. Lynne
Howell
,
Gideon J.
Davies
,
Herman S.
Overkleeft
Diamond Proposal Number(s):
[32736]
Open Access
Abstract: During infection, the human opportunistic pathogen Pseudomonas aeruginosa forms protective biofilms, whose matrix consists of proteins, nucleic acids, and polysaccharides such as alginate, Psl, and Pel. Psl, a polymeric pentasaccharide composed of mannose, rhamnose, and glucose, is produced during the early stages of biofilm formation, serving as a protective barrier against antibiotics and the immune system. The Psl biosynthesis gene cluster, besides encoding various glycosyltransferases, also includes an endoglycosidase, PslG. Here, we show, by activity-based protein profiling, structural studies on enzyme–inhibitor complexes, and defined substrate processing, that PslG is not, as previously suggested, an endo-β-mannosidase but instead a retaining endo-β-glucosidase. This insight allows the design of both competitive and covalent PslG inhibitors, as we show for repeating pentasaccharide mimetics featuring either a reducing end deoxynojirimycin or cyclophellitol moiety. This work provides valuable tools to deepen the understanding of Psl biosynthesis, its function in biofilm formation, and its contribution to antibiotic resistance. We demonstrate the enzyme’s actual endo−β–glucosidase activity, a means to monitor PslG activity in P. aeruginosa biofilms, and a blueprint for inhibitor design.
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Feb 2025
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I20-Scanning-X-ray spectroscopy (XAS/XES)
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Clorice R.
Reinhardt
,
Juliet A.
Lee
,
Lauren
Hendricks
,
Tierani
Green
,
Lily
Kunczynski
,
August Jaunzarins
Roberts
,
Naomi
Miller
,
Noga
Rafalin
,
Heather J.
Kulik
,
Christopher J.
Pollock
,
Rachel N.
Austin
Diamond Proposal Number(s):
[34781]
Abstract: Alkane monooxygenase (AlkB) is the dominant enzyme that catalyzes the oxidation of liquid alkanes in the environment. Two recent structural models derived from cryo-electron microscopy (cryo-EM) reveal an unusual active site: a histidine-rich center that binds two iron ions without a bridging ligand. To ensure that potential photoreduction and radiation damage are not responsible for the absence of a bridging ligand in the cryo-EM structures, spectroscopic methods are needed. We present the results of extended X-ray absorption fine structure (EXAFS) experiments collected under conditions where photodamage was avoided. Careful data analysis reveals an active site structure consistent with the cryo-EM structures in which the two iron ions are ligated by nine histidines and separated by at least 5 Å. The EXAFS data were used to inform structural models for molecular dynamics (MD) simulations. The MD simulations corroborate EXAFS observations that neither of the two conserved carboxylate-containing residues (E281 and D190) near the active site are likely candidates for metal ion bridging. Mutagenesis experiments, spectroscopy, and additional MD simulations were used to further explore the role of these carboxylate residues. A variant in which a carboxylate containing residue (E281) was changed to a methyl residue (E281A) showed little change in pre-edge features, consistent with the observation that it is not essential for activity and hence unlikely to serve as a bridging ligand at any point in the catalytic cycle. D190 variants had substantially diminished activity, suggesting an important role in catalysis not yet fully understood.
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Jan 2025
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I04-Macromolecular Crystallography
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Rokas
Petrenas
,
Olivia A.
Hawkins
,
Jacob F.
Jones
,
D. Arne
Scott
,
Jordan
Fletcher
,
Ulrike
Obst
,
Lucia
Lombardi
,
Fabio
Pirro
,
Graham J.
Leggett
,
Thomas A. A.
Oliver
,
Derek N.
Woolfson
Diamond Proposal Number(s):
[23269, 31440]
Open Access
Abstract: De novo protein design has advanced such that many peptide assemblies and protein structures can be generated predictably and quickly. The drive now is to bring functions to these structures, for example, small-molecule binding and catalysis. The formidable challenge of binding and orienting multiple small molecules to direct chemistry is particularly important for paving the way to new functionalities. To address this, here we describe the design, characterization, and application of small-molecule:peptide ternary complexes in aqueous solution. This uses α-helical barrel (αHB) peptide assemblies, which comprise 5 or more α helices arranged around central channels. These channels are solvent accessible, and their internal dimensions and chemistries can be altered predictably. Thus, αHBs are analogous to “molecular flasks” made in supramolecular, polymer, and materials chemistry. Using Förster resonance energy transfer as a readout, we demonstrate that specific αHBs can accept two different organic dyes, 1,6-diphenyl-1,3,5-hexatriene and Nile red, in close proximity. In addition, two anthracene molecules can be accommodated within an αHB to promote anthracene photodimerization. However, not all ternary complexes are productive, either in energy transfer or photodimerization, illustrating the control that can be exerted by judicious choice and design of the αHB.
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Jan 2025
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[29890]
Open Access
Abstract: A key feature of coordination cages is the dynamic nature of their coordinative bonds, which facilitates the synthesis of complex polyhedral structures and their post-assembly modification. However, this dynamic nature can limit cage stability. Increasing cage robustness is important for real-world use cases. Here we introduce a double-bridging strategy to increase cage stability, where designed pairs of bifunctional subcomponents combine to generate rectangular tetratopic ligands within pseudo-cubic Zn8L6 cages. These cages withstand transmetalation, the addition of competing ligands, and nucleophilic imines, under conditions where their single-bridged congeners decompose. Our approach not only increases the stability and robustness of the cages while maintaining their polyhedral structure, but also enables the incorporation of additional functional units in proximity to the cavity. The double-bridging strategy also facilitates the synthesis of larger cages, which are inaccessible as single-bridged congeners.
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Nov 2024
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B22-Multimode InfraRed imaging And Microspectroscopy
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Dukula
De Alwis Jayasinghe
,
Yinlin
Chen
,
Jiangnan
Li
,
Justyna M.
Rogacka
,
Meredydd
Kippax-Jones
,
Wanpeng
Lu
,
Sergey
Sapchenko
,
Jinyue
Yang
,
Sarayute
Chansai
,
Tianze
Zhou
,
Lixia
Guo
,
Yujie
Ma
,
Longzhang
Dong
,
Daniil
Polyukhov
,
Lutong
Shan
,
Yu
Han
,
Danielle
Crawshaw
,
Xiangdi
Zeng
,
Zhaodong
Zhu
,
Lewis
Hughes
,
Mark D.
Frogley
,
Pascal
Manuel
,
Svemir
Rudic
,
Yongqiang
Chen
,
Christopher
Hardacre
,
Martin
Schroeder
,
Sihai
Yang
Open Access
Abstract: Ammonia (NH3) production in 2023 reached 150 million tons and is associated with potential concomitant production of up to 500 million tons of CO2 each year. Efforts to produce green NH3 are compromised since it is difficult to separate using conventional condensation chillers, but in situ separation with minimal cooling is challenging. While metal–organic framework materials offer some potential, they are often unstable and decompose in the presence of caustic and corrosive NH3. Here, we address these challenges by developing a pore-expansion strategy utilizing the flexible phosphonate framework, STA-12(Ni), which shows exceptional stability and capture of NH3 at ppm levels at elevated temperatures (100–220 °C) even under humid conditions. A remarkable NH3 uptake of 4.76 mmol g–1 at 100 μbar (equivalent to 100 ppm) is observed, and in situ neutron powder diffraction, inelastic neutron scattering, and infrared microspectroscopy, coupled with modeling, reveal a pore expansion from triclinic to a rhombohedral structure on cooperative binding of NH3 to unsaturated Ni(II) sites and phosphonate groups. STA-12(Ni) can be readily engineered into pellets or monoliths without losing adsorption capacity, underscoring its practical potential.
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Nov 2024
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I07-Surface & interface diffraction
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Immad
Nadeem
,
Christopher
Penschke
,
Ji
Chen
,
Xavier
Torrelles
,
Axel
Wilson
,
Hadeel
Hussain
,
Gregory
Cabailh
,
Oier
Bikondoa
,
Jameel
Imran
,
Christopher
Nicklin
,
Robert
Lindsay
,
Jorg
Zegenhagen
,
Matthew O.
Blunt
,
Angelos
Michaelides
,
Geoff
Thornton
Diamond Proposal Number(s):
[11345, 26045]
Open Access
Abstract: Metal-oxide aqueous interfaces are important in areas as varied as photocatalysis and mineral reforming. Crucial to the chemistry at these interfaces is the structure of the electrical double layer formed when anions or cations compensate for the charge arising from adsorbed H+ or OH–. This has proven extremely challenging to determine at the atomic level. In this work, we use a surface science approach, involving atomic level characterization, to determine the structure of pH-dependent model electrified interfaces of TiO2(110) with HCl and NaOH using surface X-ray diffraction (SXRD). A comparison with ab initio molecular dynamics calculations reveals the formation of surprisingly compact double layers. These involve inner-sphere bound Cl and Na ions, with respectively H+ and O–/OH– in the contact layer. Their exceptionally high electric fields will play a key role in determining the chemical reactivity.
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Nov 2024
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