A5076753690- X-ray Diffraction in Crystallography
- Crystallization and Solubility Studies
- Crystallography and molecular interactions
- Crystal structures of chemical compounds
- Machine Learning in Materials Science
- Crystal Structures and Properties
- Thermal and Kinetic Analysis
- Asymmetric Synthesis and Catalysis
- Chemical Synthesis and Analysis
- Metal-Organic Frameworks: Synthesis and Applications
- Enzyme Structure and Function
- Phenothiazines and Benzothiazines Synthesis and Activities
- Analytical Chemistry and Chromatography
- Polymer Synthesis and Characterization
- Solid-state spectroscopy and crystallography
- Chemical Thermodynamics and Molecular Structure
- Molecular spectroscopy and chirality
- Click Chemistry and Applications
- Inorganic Fluorides and Related Compounds
- Axial and Atropisomeric Chirality Synthesis
- Advanced NMR Techniques and Applications
- Drug Solubulity and Delivery Systems
- Chemical Synthesis and Characterization
- Asymmetric Hydrogenation and Catalysis
- Carbohydrate Chemistry and Synthesis
University of Reading
2016-2025
Reading Museum
2014
AbbVie (United States)
2014
Glasgow Life
2014
Unilever (United Kingdom)
2013
University of Cambridge
2013
Rutherford Appleton Laboratory
2001-2012
University of Strathclyde
2002-2011
University of Patras
2011
University of Southampton
2009
DASH is a user-friendly graphical-user-interface-driven computer program for solving crystal structures from X-ray powder diffraction data, optimized molecular structures. Algorithms multiple peak fitting, unit-cell indexing and space-group determination are included as part of the program. Molecular models can be read in number formats automatically converted to Z-matrices which flexible torsion angles identified. Simulated annealing used search global minimum space that describes agreement...
Advances made over the past decade in structure determination from powder diffraction data are reviewed with particular emphasis on algorithmic developments and successes limitations of technique. While global optimization methods have been successful solution molecular crystal structures, new required to make inorganic structures more routine. The use complementary techniques such as NMR assist is discussed potential for combined X-ray neutron verification explored. Structures that proved...
Molecular vibrations play a critical role in the charge transport properties of weakly van der Waals bonded organic semiconductors. To understand which specific phonon modes contribute most strongly to electron-phonon coupling and ensuing thermal energetic disorder some widely studied high-mobility molecular semiconductors, state-of-the-art quantum mechanical simulations vibrational constants are combined with experimental measurements low-frequency using inelastic neutron scattering...
Mechanochemical synthesis has recently emerged as a scalable "green" approach for the preparation of MOFs, but current understanding underlying reaction mechanisms is limited. In this work, an investigation pathway mechanochemical MOF-74 from ZnO and 2,5-dihydroxyterephthalic acid (H4HDTA), using DMF liquid additive, presented. The complex involves formation four short-lived intermediate phases, prior to crystallization MOF-74. crystal structures three these intermediates have been...
The state of the art in determining molecular crystal structures from powder diffraction data using a global optimisation method is illustrated with fast, automated simulated annealing approach to solving previously unknown capsaicin, thiothixene and promazine hydrochloride.
Abstract A family of 16 isomolecular salts (3‐XpyH) 2 [MX′ 4 ] (3‐XpyH=3‐halopyridinium; M=Co, Zn; X=(F), Cl, Br, (I); X′=Cl, I) each containing rigid organic cations and tetrahedral halometallate anions has been prepared characterized by X‐ray single crystal and/or powder diffraction. Their structures reflect the competition cooperation between non‐covalent interactions: NH⋅⋅⋅X′M hydrogen bonds, CX⋅⋅⋅X′M halogen bonds π–π stacking. The latter are essentially unchanged in strength across...
Abstract A genetic algorithm (GA) based method for solving crystal structures directly from powder diffraction data has been developed. The is around fitting the generated trial against measured and ability to handle flexible molecules multiple fragments. It computationally highly efficient takes full advantage of implicit parallelism GA. illustrated with solutions three varying complexity.
Hydrogen-atom transfer across the hydrogen bonds of benzoic acid dimers has been studied previously by spectroscopic and X-ray methods, but no high-resolution neutron single crystal structures have ever reported. The system is interest because hydrogen-atom dynamics change from classical Arrhenius behaviour to phonon-assisted quantum tunnelling as a function decreasing temperature. Here we present series single-crystal structure refinements at five temperatures ranging 175 K, where holds,...
Yellow crystalline salts (3-XpyH)2[CuCl4] (3-XpyH = 3-halopyridinium, X Cl, Br) lose HCl upon exposure to air in an open vessel, yielding quantitatively blue coordination compounds [CuCl2(3-Xpy)2]. The reaction is prevented if the vessel sealed, but can be driven forward under such conditions by providing a trapping agent for HCl, as aqueous solution of AgNO3. requires cleavage Cu-Cl and N-H bonds formation Cu-N bonds. metal geometry also changes from distorted tetrahedral square planar....
An algorithm for the determination of space-group symmetry a crystal from powder diffraction data, based upon probability theory, is described. Specifically, relative probabilities different extinction symbols are assessed within particular system. In general, only small number relatively highly probable and single symbol often significantly more than any other. Several examples presented to illustrate this approach.
We have applied a combination of spectroscopic and diffraction methods to study the adduct formed between squaric acid bypridine, which has been postulated exhibit proton transfer associated with single-crystal phase transition at ca. 450 K. A X-ray very-high flux powder neutron data confirmed that does from base in high-temperature form. Powder measurements demonstrated was reversible but significant kinetic energy barrier must be overcome revert original structure. Computational modeling...
Two novel sodium salts of the antibiotic ciprofloxacin were crystallised at pressures 0.25 and 0.6 GPa subsequently recovered to ambient pressure. The structures are first reported examples chelating a Group IA monovalent cation. Ambient-pressure crystallisation same solution used for high-pressure experiments, yielded crystals known hexahydrate. In parallel study, previously unknown structure anhydrous was determined from powder diffraction data. described compared using XPac method.
Hydrogen chloride gas (HCl) is absorbed (and reversibly released) by a nonporous crystalline solid, [CuCl2(3-Clpy)2] (3-Clpy = 3-chloropyridine), under ambient conditions leading to conversion from the blue coordination compound yellow salt (3-ClpyH)2[CuCl4]. These reactions require substantial motions within solid including change in copper environment square planar tetrahedral. This process also involves cleavage of covalent bond gaseous molecules (H−Cl) and bonds molecular (Cu−N)...
The use of high-energy X-ray total scattering coupled with pair distribution function analysis produces unique structural fingerprints from amorphous and nanostructured phases the pharmaceuticals carbamazepine indomethacin. advantages such facility-based experiments over laboratory-based ones are discussed technique is illustrated characterisation a melt-quenched sample as nanocrystalline (4.5 nm domain diameter) version form III.
Abstract We report the first NMR and X‐ray diffraction (XRD) structures of an unusual 13/11‐helix (alternating i, i+1 {NH−O=C} i+3 {C=O−H−N} H‐bonds) formed by a heteromeric 1 : sequence α‐ δ‐amino acids, demonstrate application this framework towards catalysis. Whilst intramolecular hydrogen bonds (IMHBs) are clear driver helix formation in system, we also observe apolar interaction between ethyl residue one acid cyclohexyl group next δ‐residue that seems to stabilize type over another. To...
The structure of racemic ibuprofen [α-methyl-4-(2-methylpropyl)benzeneacetic acid], C13H18O2, has been refined using single-crystal pulsed neutron diffraction data collected at 100 K. Accurate positional and anisotropic displacement (vibration) parameters have determined for all 33 atoms the hydrogen-bond geometry dimeric crystal-packing motif is well defined.
The crystal structures of 35 molecular compounds have been redetermined from laboratory monochromatic capillary transmission X-ray powder diffraction data using the simulated-annealing approach embodied within DASH structure solution package. represent industrially relevant areas (pharmaceuticals; metal coordination compounds; nonlinear optical materials; dyes) in which research groups this multi-centre study are active. molecules were specifically selected to form a series degree structural...
At long last, the crystal structure of metastable form benzamide, whose existence has been known for over 170 years, finally solved by using a combination in situ crystallization, high-speed synchrotron X-ray powder diffraction, and global-optimization methods determination (see picture).
Hydrogen bonding leads the way: Reaction of nonporous crystalline coordination compound 1 with HCl gas results in conversion into salt 2 (see picture) following chemisorption and insertion CuN bonds. Powder diffraction studies show that [CuBr2Cl2]2− ions formed are reoriented to maximize strength hydrogen bonds halogen by preferentially involving Cl rather than Br ligands as acceptor sites.
The stereoselective construction of complex molecules with multiple stereogenicity in a single step represents an extremely useful, but challenging approach to complexity chemical synthesis. development organocatalytic cascade processes has proven useful these studies, reports where four or more stereocentres are created from just two achiral reagents rare. Herein we report the novel asymmetric domino Michael-Michael reaction between nitrohex-4-enoates and nitro-olefins generate cyclohexanes...
The constant increase in cardiovascular disease rate coupled with significant drawbacks of existing therapies emphasise the necessity to improve therapeutic strategies. Natural flavonoids exert innumerable pharmacological effects humans. Here, we demonstrate chrysin, a natural flavonoid found largely honey and passionflower on modulation platelet function, haemostasis thrombosis. Chrysin displayed inhibitory isolated platelets, however, its activity was substantially reduced under...