I11-High Resolution Powder Diffraction
I19-Small Molecule Single Crystal Diffraction
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Xiaoyan
Wang
,
Linjiang
Chen
,
Samantha Y.
Chong
,
Marc A.
Little
,
Yongzhen
Wu
,
Wei-hong
Zhu
,
Rob
Clowes
,
Yong
Yan
,
Martijn A.
Zwijnenburg
,
Reiner Sebastian
Sprick
,
Andrew I.
Cooper
Diamond Proposal Number(s):
[15777, 17193]
Abstract: Nature uses organic molecules for light harvesting and photosynthesis, but most man-made water splitting catalysts are inorganic semiconductors. Organic photocatalysts, while attractive because of their synthetic tunability, tend to have low quantum efficiencies for water splitting. Here we present a crystalline covalent organic framework (COF) based on a benzo-bis(benzothiophene sulfone) moiety that shows a much higher activity for photochemical hydrogen evolution than its amorphous or semicrystalline counterparts. The COF is stable under long-term visible irradiation and shows steady photochemical hydrogen evolution with a sacrificial electron donor for at least 50 hours. We attribute the high quantum efficiency of fused-sulfone-COF to its crystallinity, its strong visible light absorption, and its wettable, hydrophilic 3.2 nm mesopores. These pores allow the framework to be dye-sensitized, leading to a further 61% enhancement in the hydrogen evolution rate up to 16.3 mmol g−1 h−1. The COF also retained its photocatalytic activity when cast as a thin film onto a support.
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Oct 2018
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I11-High Resolution Powder Diffraction
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Kasper S.
Pedersen
,
Panagiota
Perlepe
,
Michael L.
Aubrey
,
Daniel N.
Woodruff
,
Sebastian E.
Reyes-lillo
,
Anders
Reinholdt
,
Laura
Voigt
,
Zheshen
Li
,
Kasper
Borup
,
Mathieu
Rouzières
,
Dumitru
Samohvalov
,
Fabrice
Wilhelm
,
Andrei
Rogalev
,
Jeffrey B.
Neaton
,
Jeffrey R.
Long
,
Rodolphe
Clérac
Diamond Proposal Number(s):
[13284]
Abstract: The unique properties of graphene, transition-metal dichalcogenides and other two-dimensional (2D) materials have boosted interest in layered coordination solids. In particular, 2D materials that behave as both conductors and magnets could find applications in quantum magnetoelectronics and spintronics. Here, we report the synthesis of CrCl2(pyrazine)2, an air-stable layered solid, by reaction of CrCl2 with pyrazine (pyz). This compound displays a ferrimagnetic order below ∼55 K, reflecting the presence of strong magnetic interactions. Electrical conductivity measurements demonstrate that CrCl2(pyz)2 reaches a conductivity of 32 mS cm–1 at room temperature, which operates through a 2D hopping-based transport mechanism. These properties are induced by the redox-activity of the pyrazine ligand, which leads to a smearing of the Cr 3d and pyrazine π states. We suggest that the combination of redox-active ligands and reducing paramagnetic metal ions represents a general approach towards tuneable 2D materials that consist of charge-neutral layers and exhibit both long-range magnetic order and high electronic conductivity.
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Oct 2018
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[17379]
Abstract: The simultaneous synthesis of a molecular nine-crossing composite knot that contains three trefoil tangles of the same handedness and a 9 3 7
973
link (a type of cyclic [3]catenane topologically constrained to always have at least three twists within the links) is reported. Both compounds contain high degrees of topological writhe (w = 9), a structural feature of supercoiled DNA. The entwined products are generated from the cyclization of a hexameric Fe(ii) circular helicate by ring-closing olefin metathesis, with the mixture of topological isomers formed as a result of different ligand connectivity patterns. The metal-coordinated composite knot was isolated by crystallization, the topology unambiguously proven by tandem mass spectrometry, with X-ray crystallography confirming that the 324-atom loop crosses itself nine times with matching handedness (all Δ or all Λ) at every metal centre within each molecule. Controlling the connectivity of the ligand end groups on circular metal helicate scaffolds provides an effective synthetic strategy for the stereoselective synthesis of composite knots and other complex molecular topologies.
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Sep 2018
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I19-Small Molecule Single Crystal Diffraction
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J.
López-cabrelles
,
S.
Mañas-valero
,
I. J.
Vitorica-yrezabal
,
P. J.
Bereciartua
,
J. A.
Rodríguez-velamazán
,
J. C.
Waerenborgh
,
B. J. C.
Vieira
,
D.
Davidovikj
,
P. G.
Steeneken
,
H. S. J.
Van Der Zant
,
G.
Mínguez Espallargas
,
E.
Coronado
Diamond Proposal Number(s):
[17379]
Abstract: Chemical functionalization is a powerful approach to tailor the physical and chemical properties of two-dimensional (2D) materials, increase their processability and stability, tune their functionalities and, even, create new 2D materials. This is typically achieved through post-synthetic functionalization by anchoring molecules on the surface of an exfoliated 2D crystal, but it inevitably alters the long-range structural order of the material. Here we present a pre-synthetic approach that allows the isolation of crystalline, robust and magnetic functionalized monolayers of coordination polymers. A series of five isostructural layered magnetic coordination polymers based on Fe(ii) centres and different benzimidazole derivatives (bearing a Cl, H, CH3, Br or NH2 side group) were first prepared. On mechanical exfoliation, 2D materials are obtained that retain their long-range structural order and exhibit good mechanical and magnetic properties. This combination, together with the possibility to functionalize their surface at will, makes them good candidates to explore magnetism in the 2D limit and to fabricate mechanical resonators for selective gas sensing.
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Aug 2018
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I11-High Resolution Powder Diffraction
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Lauren N.
Mchugh
,
Matthew J.
Mcpherson
,
Laura J.
Mccormick
,
Samuel A.
Morris
,
Paul S.
Wheatley
,
Simon J.
Teat
,
David
Mckay
,
Daniel M.
Dawson
,
Charlotte E. F.
Sansome
,
Sharon E.
Ashbrook
,
Corinne A.
Stone
,
Martin W.
Smith
,
Russell E.
Morris
Abstract: Highly porous metal–organic frameworks (MOFs), which have undergone exciting developments over the past few decades, show promise for a wide range of applications. However, many studies indicate that they suffer from significant stability issues, especially with respect to their interactions with water, which severely limits their practical potential. Here we demonstrate how the presence of ‘sacrificial’ bonds in the coordination environment of its metal centres (referred to as hemilability) endows a dehydrated copper-based MOF with good hydrolytic stability. On exposure to water, in contrast to the indiscriminate breaking of coordination bonds that typically results in structure degradation, it is non-structural weak interactions between the MOF’s copper paddlewheel clusters that are broken and the framework recovers its as-synthesized, hydrated structure. This MOF retained its structural integrity even after contact with water for one year, whereas HKUST-1, a compositionally similar material that lacks these sacrificial bonds, loses its crystallinity in less than a day under the same conditions.
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Aug 2018
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B23-Circular Dichroism
I22-Small angle scattering & Diffraction
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Diamond Proposal Number(s):
[11321, 13761, 13768]
Abstract: The increasing requirement to produce platform chemicals and fuels from renewable sources means advances in biocatalysis are rapidly becoming a necessity. Biomass is widely used in nature as a source of energy and as chemical building blocks. However, recalcitrance towards traditional chemical processes and solvents provides a significant barrier to widespread utility. Here, by optimizing enzyme solubility in ionic liquids, we have discovered solvent-induced substrate promiscuity of glucosidase, demonstrating an unprecedented example of homogeneous enzyme bioprocessing of cellulose. Specifically, chemical modification of glucosidase for solubilization in ionic liquids can increase thermal stability to up to 137 °C, allowing for enzymatic activity 30 times greater than is possible in aqueous media. These results establish that through a synergistic combination of chemical biology (enzyme modification) and reaction engineering (solvent choice), the biocatalytic capability of enzymes can be intensified: a key step towards the full-scale deployment of industrial biocatalysis.
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Jun 2018
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I04-1-Macromolecular Crystallography (fixed wavelength)
I04-Macromolecular Crystallography
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Aurélie
Mousnier
,
Andrew S.
Bell
,
Dawid P.
Swieboda
,
Julia
Morales-sanfrutos
,
Inmaculada
Perez-dorado
,
James A.
Brannigan
,
Joseph
Newman
,
Markus
Ritzefeld
,
Jennie A.
Hutton
,
Anabel
Guedán
,
Amin S.
Asfor
,
Sean W.
Robinson
,
Iva
Hopkins-navratilova
,
Anthony J.
Wilkinson
,
Sebastian L.
Johnston
,
Robin J.
Leatherbarrow
,
Tobias J.
Tuthill
,
Roberto
Solari
,
Edward W.
Tate
Diamond Proposal Number(s):
[12579, 7864, 9948]
Abstract: Rhinoviruses (RVs) are the pathogens most often responsible for the common cold, and are a frequent cause of exacerbations in asthma, chronic obstructive pulmonary disease and cystic fibrosis. Here we report the discovery of IMP-1088, a picomolar dual inhibitor of the human N-myristoyltransferases NMT1 and NMT2, and use it to demonstrate that pharmacological inhibition of host-cell N-myristoylation rapidly and completely prevents rhinoviral replication without inducing cytotoxicity. The identification of cooperative binding between weak-binding fragments led to rapid inhibitor optimization through fragment reconstruction, structure-guided fragment linking and conformational control over linker geometry. We show that inhibition of the co-translational myristoylation of a specific virus-encoded protein (VP0) by IMP-1088 potently blocks a key step in viral capsid assembly, to deliver a low nanomolar antiviral activity against multiple RV strains, poliovirus and foot and-mouth disease virus, and protection of cells against virus-induced killing, highlighting the potential of host myristoylation as a drug target in picornaviral infections.
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May 2018
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B18-Core EXAFS
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Urmimala
Maitra
,
Robert A.
House
,
James W.
Somerville
,
Nuria
Tapia-ruiz
,
Juan G.
Lozano
,
Niccolo
Guerrini
,
Rong
Hao
,
Kun
Luo
,
Liyu
Jin
,
Miguel A.
Pérez-osorio
,
Felix
Massel
,
David M.
Pickup
,
Silvia
Ramos
,
Xingye
Lu
,
Daniel E.
Mcnally
,
Alan V.
Chadwick
,
Feliciano
Giustino
,
Thorsten
Schmitt
,
Laurent C.
Duda
,
Matthew R.
Roberts
,
Peter G.
Bruce
Diamond Proposal Number(s):
[12559]
Abstract: The search for improved energy-storage materials has revealed Li- and Na-rich intercalation compounds to have promise as a new class of high-capacity cathodes. They exhibit capacities in excess of what would be expected from alkali-ion removal/reinsertion charge compensated by the transition-metal ions. The additional capacity is provided through charge compensation by oxygen-redox chemistry and some oxygen loss. It has been reported previously that O-redox occurs in O-2p orbitals that interact with alkali-ions in the transition-metal and alkali-ion layers (i.e. O-redox occurs in compounds containing Li+ - O2p - Li+ interactions). Na2/3[Mg0.28Mn0.72]O2 exhibits excess capacity; here we show this is also due to O-redox, despite Mg2+ residing in the transition-metal (TM) layers rather than alkali-metal ions, demonstrating that excess alkali-metal ions are not required to activate O-redox. We also show that unlike the alkali-rich compounds, Na2/3[Mg0.28Mn0.72]O2 does not lose O. Extraction of alkali ions from the alkali and TM layers in the alkali-rich compounds results in severely underbonded oxygen promoting oxygen loss, whereas Mg2+ remains in Na2/3[Mg0.28Mn0.72]O2 stabilising oxygen.
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Jan 2018
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I07-Surface & interface diffraction
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Hannah L.
Stern
,
Alexandre
Cheminal
,
Shane R.
Yost
,
Katharina
Broch
,
Sam L.
Bayliss
,
Kai
Chen
,
Maxim
Tabachnyk
,
Karl
Thorley
,
Neil
Greenham
,
Justin M.
Hodgkiss
,
John
Anthony
,
Martin
Head-gordon
,
Andrew J.
Musser
,
Akshay
Rao
,
Richard H.
Friend
Diamond Proposal Number(s):
[11220]
Abstract: Singlet exciton fission (SF), the conversion of one spin-singlet exciton (S1) into two spin-triplet excitons (T1), could provide a means to overcome the Shockley–Queisser limit in photovoltaics. SF as measured by the decay of S1 has been shown to occur efficiently and independently of temperature, even when the energy of S1 is as much as 200 meV less than that of 2T1. Here we study films of triisopropylsilyltetracene using transient optical spectroscopy and show that the triplet pair state (TT), which has been proposed to mediate singlet fission, forms on ultrafast timescales (in 300 fs) and that its formation is mediated by the strong coupling of electronic and vibrational degrees of freedom. This is followed by a slower loss of singlet character as the excitation evolves to become only TT. We observe the TT to be thermally dissociated on 10–100 ns timescales to form free triplets. This provides a model for ‘temperature-independent’ efficient TT formation and thermally activated TT separation.
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Sep 2017
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[11397]
Abstract: Natural reaction cascades control the movement of biomolecules between cellular compartments. Inspired by these systems, we report a synthetic reaction cascade employing post-assembly modification reactions to direct the partitioning of supramolecular complexes between phases. The system is composed of a self-assembled tetrazine-edged FeII8L12 cube and a maleimide-functionalized FeII4L6 tetrahedron. Norbornadiene (NBD) functions as the stimulus that triggers the cascade, beginning with the inverse-electron-demand Diels–Alder reaction of NBD with the tetrazine moieties of the cube. This reaction generates cyclopentadiene as a transient by-product, acting as a relay signal that subsequently undergoes a Diels–Alder reaction with the maleimide-functionalized tetrahedron. Cyclooctyne can selectively inhibit the cascade by outcompeting NBD as the initial trigger. Initiating the cascade with 2-octadecyl NBD leads to selective alkylation of the tetrahedron upon cascade completion. The increased lipophilicity of the C18-tagged tetrahedron drives this complex into a non-polar phase, allowing its isolation from the initially inseparable mixture of complexes.
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Aug 2017
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