Co-reporter:Arnaud Desmedt;Simon J. Kitchin;François Guillaume;Rik R. Tykwinski;Mingcan Xu;Miguel A. Gonzalez
The Journal of Physical Chemistry C October 9, 2008 Volume 112(Issue 40) pp:15870-15879
Publication Date(Web):2017-2-22
DOI:10.1021/jp8042889
Ammonium cyanate is well-known to undergo a solid-state reaction to form urea. Knowledge of fundamental physicochemical properties of solid ammonium cyanate is a prerequisite for understanding this solid-state chemical transformation, and this paper presents a comprehensive study of the dynamic properties of the ammonium cation in this material. The techniques used—incoherent quasielastic neutron scattering (QENS) and solid-state 2H NMR spectroscopy—provide insights into dynamic properties across a complementary range of time scales. The QENS investigations (carried out on a sample with natural isotopic abundances) employed two different spectrometers, allowing different experimental resolutions to be probed. The 2H NMR experiments (carried out on the deuterated material ND4+OCN−) involved both 2H NMR line shape analysis and 2H NMR spin−lattice relaxation time measurements. The results of both the QENS and 2H NMR studies demonstrate that the ammonium cation exhibits reorientational dynamics across a wide temperature range, and several dynamic models (based on knowledge of the crystal structure of ammonium cyanate) were considered in this work. It is found that a tetrahedral jump model for the dynamics of the ammonium cation provides the best description for both the QENS and 2H NMR data, and there is excellent agreement between the values of activation parameters established from these two experimental approaches, with estimated activation energies of 22.6 ± 2.1 kJ mol−1 from QENS and 21.9 ± 1.0 kJ mol−1 from 2H NMR spin−lattice relaxation time measurements. The wider implications of the results from this work are discussed.
Co-reporter:Kenneth D. M. Harris;Zhongfu Zhou
The Journal of Physical Chemistry C October 23, 2008 Volume 112(Issue 42) pp:16186-16188
Publication Date(Web):2017-2-22
DOI:10.1021/jp807372j
We report the design of a new quasicrystalline material constructed from discrete molecular building units and based on the Penrose tiling as the basic structural template. The quasicrystal comprises three different molecular components, which is shown to represent the minimum number of components required for a molecular representation of the Penrose tiling. The density of this molecular quasicrystal is comparable to typical densities of crystalline organic materials. With regard to both the number of molecular components and density, the experimental realization of the molecular quasicrystal reported in this paper is considerably more promising than a seven-component, low-density representation of the Penrose tiling that represents the only previous reported example of a molecular quasicrystal.
Co-reporter:Fang Guo;Javier Martí-Rujas;Zhigang Pan;Colan E. Hughes
The Journal of Physical Chemistry C December 18, 2008 Volume 112(Issue 50) pp:19793-19796
Publication Date(Web):2017-2-22
DOI:10.1021/jp808254f
Hitherto, direct structural characterization of polycrystalline product phases obtained in solid state polymerization reactions has been limited by the lack of appropriate experimental techniques for structure determination. This paper demonstrates the opportunity to apply modern powder X-ray diffraction techniques for carrying out complete structure determination in such cases, by reporting the structural properties of the polymer phase obtained in the solid state photopolymerization reaction of 2,5-distyrylpyrazine. The structure of the polymer phase, for which structure solution was carried out using the direct-space genetic algorithm technique followed by Rietveld refinement, demonstrates directly the topochemical nature of this solid state reaction.
Co-reporter:Vasileios G. Charalampopoulos, Benson M. KariukiKenneth D.M. Harris
Crystal Growth & Design 2017 Volume 17(Issue 2) pp:
Publication Date(Web):December 22, 2016
DOI:10.1021/acs.cgd.6b01644
We report the preparation and structural properties of complexes of metal halides and thiourea with composition MX[thiourea]4 (MX = KBr, KI, RbI, CsI) together with the mixed-halide materials KBrnI1–n[thiourea]4 (0 < n < 1) and the mixed-metal materials KnCs1–nI[thiourea]4 (0 < n < 1). These materials are isostructural with a tetragonal structure (space group P4/mnc) characterized by M+[thiourea]4 coordination columns along the 4-fold axis and halide anions located in channels in the region of space between adjacent columns and running parallel to the columns. For the mixed-halide materials, the stoichiometry KBrnI1–n[thiourea]4 depends on the bromide/iodide ratio in the crystallization solution; the crystalline complexes have a higher bromide/iodide ratio than the crystallization solution, indicating preferential incorporation of bromide within the complex. Soaking crystals of KBr0.61I0.39[thiourea]4 in iodide-containing solutions leads to halide exchange with the iodide to bromide ratio increasing relative to that of the parent crystal. Further experiments produced no evidence that these thiourea complexes can accommodate extended polyiodide networks.
Co-reporter:Miri Zilka;Dmytro V. Dudenko;Colan E. Hughes;P. Andrew Williams;Simone Sturniolo;W. Trent Franks;Chris J. Pickard;Jonathan R. Yates;Steven P. Brown
Physical Chemistry Chemical Physics 2017 vol. 19(Issue 38) pp:25949-25960
Publication Date(Web):2017/10/04
DOI:10.1039/C7CP04186A
This paper explores the capability of using the DFT-D ab initio random structure searching (AIRSS) method to generate crystal structures of organic molecular materials, focusing on a system (m-aminobenzoic acid; m-ABA) that is known from experimental studies to exhibit abundant polymorphism. Within the structural constraints selected for the AIRSS calculations (specifically, centrosymmetric structures with Z = 4 for zwitterionic m-ABA molecules), the method is shown to successfully generate the two known polymorphs of m-ABA (form III and form IV) that have these structural features. We highlight various issues that are encountered in comparing crystal structures generated by AIRSS to experimental powder X-ray diffraction (XRD) data and solid-state magic-angle spinning (MAS) NMR data, demonstrating successful fitting for some of the lowest energy structures from the AIRSS calculations against experimental low-temperature powder XRD data for known polymorphs of m-ABA, and showing that comparison of computed and experimental solid-state NMR parameters allows different hydrogen-bonding motifs to be discriminated.
Co-reporter:Colan E. Hughes;G. N. Manjunatha Reddy;Stefano Masiero;Steven P. Brown;P. Andrew Williams
Chemical Science (2010-Present) 2017 vol. 8(Issue 5) pp:3971-3979
Publication Date(Web):2017/05/03
DOI:10.1039/C7SC00587C
Derivatives of guanine exhibit diverse supramolecular chemistry, with a variety of distinct hydrogen-bonding motifs reported in the solid state, including ribbons and quartets, which resemble the G-quadruplex found in nucleic acids with sequences rich in guanine. Reflecting this diversity, the solid-state structural properties of 3′,5′-bis-O-decanoyl-2′-deoxyguanosine, reported in this paper, reveal a hydrogen-bonded guanine ribbon motif that has not been observed previously for 2′-deoxyguanosine derivatives. In this case, structure determination was carried out directly from powder XRD data, representing one of the most challenging organic molecular structures (a 90-atom molecule) that has been solved to date by this technique. While specific challenges were encountered in the structure determination process, a successful outcome was achieved by augmenting the powder XRD analysis with information derived from solid-state NMR data and with dispersion-corrected periodic DFT calculations for structure optimization. The synergy of experimental and computational methodologies demonstrated in the present work is likely to be an essential feature of strategies to further expand the application of powder XRD as a technique for structure determination of organic molecular materials of even greater complexity in the future.
Co-reporter:Manal A. Khoj, Colan E. Hughes, Kenneth D. M. HarrisBenson M. Kariuki
Crystal Growth & Design 2017 Volume 17(Issue 3) pp:
Publication Date(Web):January 18, 2017
DOI:10.1021/acs.cgd.6b01675
The formation and structural properties of solid solutions containing 3-chloro-trans-cinnamic acid (3-ClCA) and 3-bromo-trans-cinnamic acid (3-BrCA) are explored across a range of compositions. Two distinct γ-type structures of 3-ClCA/3-BrCA solid solutions and two distinct β-type structures of 3-ClCA/3-BrCA solid solutions are reported and structurally characterized. One of the γ-type structures is isostructural with the known γ polymorphs of pure 3-ClCA and pure 3-BrCA, whereas the other γ-type structure has not been observed previously for either pure 3-ClCA or pure 3-BrCA (representing a rare case in which the structure of the solid solution is not known for the pure phases of either of the constituent molecules). One of the β-type structures of the 3-ClCA/3-BrCA solid solutions is similar to the β polymorph of pure 3-ClCA, whereas the other β-type structure is similar to the β polymorph of pure 3-BrCA. The specific β-type structure formed is found to depend on the relative amounts of 3-BrCA and 3-ClCA in the solid solution. UV irradiation of the β-type 3-ClCA/3-BrCA solid solution with 1:1 composition yields three different photodimers, with substituents {Cl,Cl}, {Cl,Br}, or {Br,Br} in the approximate ratio 1:2:1 respectively, consistent with the occurrence of a topochemical reaction in a solid solution with a random distribution of 3-ClCA and 3-BrCA molecules.
Co-reporter:Kenneth D. M. Harris;Colan E. Hughes;Gregory R. Edwards-Gau;P. Andrew Williams
Acta Crystallographica Section C 2017 Volume 73(Issue 3) pp:137-148
Publication Date(Web):
DOI:10.1107/S2053229616019811
Solid-state NMR spectroscopy is a well-established and versatile technique for studying the structural and dynamic properties of solids, and there is considerable potential to exploit the power and versatility of solid-state NMR for in-situ studies of chemical processes. However, a number of technical challenges are associated with adapting this technique for in-situ studies, depending on the process of interest. Recently, an in-situ solid-state NMR strategy for monitoring the evolution of crystallization processes has been developed and has proven to be a promising approach for identifying the sequence of distinct solid forms present as a function of time during crystallization from solution, and for the discovery of new polymorphs. The latest development of this technique, called `CLASSIC' NMR, allows the simultaneous measurement of both liquid-state and solid-state NMR spectra as a function of time, thus yielding complementary information on the evolution of both the liquid phase and the solid phase during crystallization from solution. This article gives an overview of the range of NMR strategies that are currently available for in-situ studies of crystallization processes, with examples of applications that highlight the potential of these strategies to deepen our understanding of crystallization phenomena.
Co-reporter:John Meurig Thomas and Kenneth D. M. Harris
Energy & Environmental Science 2016 vol. 9(Issue 3) pp:687-708
Publication Date(Web):06 Jan 2016
DOI:10.1039/C5EE03461B
This review provides a wide-ranging summary of several aspects of heterogeneous catalysis and its impact on the increasing need to generate more energy, less CO2 and the production of more commodities required by an expanding world population. Particular attention is paid to the options (some of which are already a practical reality) now available for the use of anthropogenic CO2 as a source for the production of platform chemicals required to sustain civilized life. In this connection, Rubisco-inspired methods of utilizing CO2 are discussed, as is the utilization of algae to yield ethanol and O2 from water, CO2 and sunlight. In addition, the increasing use of methanol (derived from CO2) as an energy vector, as well as a source of ethene and propene (which are in growing worldwide demand), is adumbrated. As far as strategies for the design of new solid catalysts are concerned, summarizing accounts are given of the emerging popularity and recent successes of supported “single-atom”, chemo-selective catalysts (of Pt, Pd, Ir and Au), of so-called “single-atom alloy” catalysts for selective hydrogenations, and of monophasic single-site heterogeneous catalysts (SSHCs) for a range of chemical processes, some of which have already been commercialized. SSHCs can, in general, be assembled from earth-abundant elements (C, N, O, Mg, Al, P, Fe), and are effective for shape-selective, regio-selective and enantio-selective catalytic conversions. We also briefly discuss the prospect of converting anthropogenic CO2 into CH4, and touch upon the action needed to reduce atmospheric CO2 so as to fulfil the aims of the recent (December 2015) UN Climate Change Conference in Paris (COP-21).
Co-reporter:Benjamin A. Palmer, Stephen P. Collins, Jürg Hulliger, Colan E. Hughes, and Kenneth D. M. Harris
Journal of the American Chemical Society 2016 Volume 138(Issue 50) pp:16188-16191
Publication Date(Web):December 5, 2016
DOI:10.1021/jacs.6b09054
To demonstrate that measurements of X-ray linear dichroism are effective for determining bond orientations in disordered materials, we report the first observation of X-ray linear dichroism at the iodine L1-edge. The iodine-containing molecular solid studied in this work was the inclusion compound containing 4,4′-diiodobiphenyl guest molecules in the perhydrotriphenylene host structure. In this material, the guest substructure does not exhibit three-dimensional ordering, and thus diffraction-based techniques do not provide insights on the orientational properties of the guest molecules. Iodine L1-edge X-ray absorption spectra, recorded as a function of orientation of a single crystal of the material, exhibit significant dichroism (whereas no dichroism is observed at the iodine L2- and L3-edges). From quantitative analysis of the X-ray dichroism, the orientational properties of the C–I bonds within this material are established. The results pave the way for applying X-ray dichroism to determine molecular orientational properties of other materials, especially for partially ordered materials such as liquid crystals, confined liquids, and disordered crystalline phases, for which diffraction techniques may not be applicable.
Co-reporter:Abigail E. Watts, Keisuke Maruyoshi, Colan E. Hughes, Steven P. Brown, and Kenneth D. M. Harris
Crystal Growth & Design 2016 Volume 16(Issue 4) pp:1798-1804
Publication Date(Web):March 8, 2016
DOI:10.1021/acs.cgd.6b00016
We report the crystal structure of the anhydrous phase of cimetidine hydrochloride, determined directly from powder X-ray diffraction data. The material was prepared by dehydration of the readily obtained monohydrate form of cimetidine hydrochloride, the only form for which a crystal structure has previously been reported. As such, solid-state dehydration processes typically yield the product phase as a microcrystalline powder, and structure determination was carried out directly from powder X-ray diffraction data, using the direct-space genetic algorithm technique for structure solution followed by Rietveld refinement. The structure determined from powder X-ray diffraction was further validated by calculating solid-state 13C NMR data for the crystal structure (using first-principles periodic DFT techniques within the GIPAW approach) and assessing the quality of agreement with the corresponding experimental solid-state 13C CPMAS NMR data. This strategy provides a robust vindication of the correctness of the crystal structure by assessing the quality of agreement of the structure both with experimental powder X-ray diffraction data and with experimental solid-state 13C NMR data.
Co-reporter:Kenneth D. M. Harris
Applied Petrochemical Research 2016 Volume 6( Issue 3) pp:295-306
Publication Date(Web):2016 September
DOI:10.1007/s13203-016-0152-3
Solid-state NMR spectroscopy is a powerful technique for studying structural and dynamic properties of solids and has considerable potential to be exploited for in situ studies of chemical processes. However, adapting solid-state NMR techniques and instrumentation for in situ applications are often associated with technical challenges, and for this reason, the opportunities remain underexploited. This paper highlights two experimental strategies that we have developed in recent years for in situ solid-state NMR investigations of solid-state processes. One technique is focused on probing details of the time evolution of materials formation processes, and the other technique is focused on understanding the time evolution of adsorption processes in microporous and mesoporous solid host materials. Each of these in situ solid-state NMR techniques has significant prospects for applications in areas relating to heterogeneous catalysis.
Co-reporter:P. Andrew Williams
The Journal of Physical Chemistry C 2016 Volume 120(Issue 17) pp:9385-9392
Publication Date(Web):April 8, 2016
DOI:10.1021/acs.jpcc.5b12420
The crystal structure of l-lysine was reported very recently and represented the final member of the set of 20 directly encoded proteinogenic amino acids to have a crystal structure of the enantiomerically pure form determined. Under ambient conditions, l-lysine has a strong propensity to undergo hydration by incorporation of water into the crystal structure, and dehydration under rigorously dry conditions is required to obtain anhydrous l-lysine. In the present paper, we explore the hydration of l-lysine, which has led to the identification and characterization of a hemihydrate phase and a monohydrate phase. As the hydration processes give rise to microcrystalline powder samples of the hydrate phases, powder X-ray diffraction has been exploited for crystal structure determination of both l-lysine hemihydrate and l-lysine monohydrate. The conditions for interconversion between anhydrous l-lysine and the two hydrate phases have been investigated by dynamic vapor sorption measurements, leading to an understanding of the hydration/dehydration behavior in this system.
Co-reporter:Kilingaru I. Shivakumar, Yuncheng Yan, Colan E. Hughes, David C. Apperley, Kenneth D. M. Harris, and Gangadhar J. Sanjayan
Crystal Growth & Design 2015 Volume 15(Issue 4) pp:1583-1587
Publication Date(Web):March 11, 2015
DOI:10.1021/acs.cgd.5b00277
We report the solvent-mediated supramolecular assembly of pillar[5]quinone (P[5]Q), a symmetric cyclamer containing five benzoquinone moieties bridged by five alternating methylene units. The supramolecular assembly of P[5]Q is shown to be facilitated by 1,1,2,2-tetrachloroethane (TCE) as solvent, producing a microcrystalline solvate material P[5]Q·2TCE with a fluffy texture. Optical and electron microscopy reveal that this material has a rod-shaped morphology, extending to several micrometers in length. Due to the microcrystalline nature of the material, structure determination was carried out directly from powder X-ray diffraction data, augmented by high-resolution solid-state 13C NMR. The two crystallographically distinct TCE molecules occupy different types of void in the structure and have different dynamic properties. Crystallization of P[5]Q was attempted from a large number of different solvents, but only TCE was found to facilitate the formation of a crystalline phase. Indeed, features of the crystal structure suggest that the TCE component plays an important role in promoting the columnar assembly of P[5]Q molecules.
Co-reporter:Yating Zhou, Fang Guo, Colan E. Hughes, Duncan L. Browne, Thomas R. Peskett, and Kenneth D. M. Harris
Crystal Growth & Design 2015 Volume 15(Issue 6) pp:2901
Publication Date(Web):May 5, 2015
DOI:10.1021/acs.cgd.5b00331
Members of a homologous family of 1:2 co-crystals comprising even-chain α,ω-dihydroxyalkanes and urea have been reported previously to fall into three well-defined structure types, although surprisingly polymorphism was not observed for any member of this series. Here we report the discovery of the first examples of polymorphism within this family of materials, specifically for 1,6-dihydroxyhexane-(urea)2 and 1,8-dihydroxyoctane-(urea)2. The new polymorphs have been prepared by mechanochemical milling, and the crystal structures have been determined directly from powder X-ray diffraction data. On the basis of periodic density functional theory calculations, the new polymorphs are assigned as metastable with respect to the polymorphs reported previously. Under ambient conditions, the new polymorph of 1,6-dihydroxyhexane-(urea)2 transforms to the previously known polymorph over a matter of days. However, the new polymorph of 1,8-dihydroxyoctane-(urea)2 has significantly greater kinetic stability, which can be rationalized on the basis of the specific structural reorganization required to transform to the previously known polymorph.
Co-reporter:Kenneth D.M. Harris, Colan E. Hughes, P. Andrew Williams
Solid State Nuclear Magnetic Resonance 2015 Volume 65() pp:107-113
Publication Date(Web):February 2015
DOI:10.1016/j.ssnmr.2014.11.004
Crystallization processes play a crucial role in many aspects of biological and physical sciences. Progress in deepening our fundamental understanding of such processes relies, to a large extent, on the development and application of new experimental strategies that allow direct in-situ monitoring of the process. In this paper, we give an overview of an in-situ solid-state NMR strategy that we have developed in recent years for monitoring the time-evolution of different polymorphic forms (or other solid forms) that arise as the function of time during crystallization from solution. The background to the strategy is described and several examples of the application of the technique are highlighted, focusing on both the evolution of different polymorphs during crystallization and the discovery of new polymorphs.
Co-reporter:Dr. P. Andrew Williams;Dr. Colan E. Hughes ; Kenneth D. M. Harris
Angewandte Chemie 2015 Volume 127( Issue 13) pp:
Publication Date(Web):
DOI:10.1002/ange.201411520
Abstract
During the last 75 years, crystal structures have been reported for 19 of the 20 directly encoded proteinogenic amino acids in their natural (enantiomerically pure) form. The crystal structure is now reported for the final member of this set: L-lysine. As crystalline L-lysine has a strong propensity to incorporate water under ambient atmospheric conditions to form a hydrate phase, the pure (non-hydrate) crystalline phase can be obtained only by dehydration under rigorously anhydrous conditions, resulting in a microcrystalline powder sample. For this reason, modern powder X-ray diffraction methods have been exploited to determine the crystal structure in this final, elusive case.
Co-reporter:Dr. P. Andrew Williams;Dr. Colan E. Hughes ; Kenneth D. M. Harris
Angewandte Chemie International Edition 2015 Volume 54( Issue 13) pp:
Publication Date(Web):
DOI:10.1002/anie.201411520
Abstract
During the last 75 years, crystal structures have been reported for 19 of the 20 directly encoded proteinogenic amino acids in their natural (enantiomerically pure) form. The crystal structure is now reported for the final member of this set: L-lysine. As crystalline L-lysine has a strong propensity to incorporate water under ambient atmospheric conditions to form a hydrate phase, the pure (non-hydrate) crystalline phase can be obtained only by dehydration under rigorously anhydrous conditions, resulting in a microcrystalline powder sample. For this reason, modern powder X-ray diffraction methods have been exploited to determine the crystal structure in this final, elusive case.
Co-reporter:Benjamin A. Palmer; Gregory R. Edwards-Gau; Benson M. Kariuki; Kenneth D. M. Harris; Igor P. Dolbnya; Stephen P. Collins;John P. Sutter
The Journal of Physical Chemistry Letters 2015 Volume 6(Issue 3) pp:561-567
Publication Date(Web):January 16, 2015
DOI:10.1021/jz502652n
The X-ray birefringence imaging (XBI) technique, reported very recently, is a sensitive tool for spatially resolved mapping of the local orientational properties of anisotropic materials. In this paper, we report the first XBI measurements on materials that undergo anisotropic molecular dynamics. Using incident linearly polarized X-rays with energy close to the Br K-edge, the X-ray birefringence is dictated by the orientational properties of the C–Br bonds in the material. We focus on two materials (urea inclusion compounds containing 1,8-dibromooctane and 1,10-dibromodecane guest molecules) for which the reorientational dynamics of the brominated guest molecules (and hence the reorientational dynamics of the C–Br bonds) are already well characterized by other experimental techniques. The XBI results demonstrate clearly that, for the anisotropic molecular dynamics in these materials, the effective X-ray optic axis for the X-ray birefringence phenomenon is the time-averaged resultant of the orientational distribution of the C–Br bonds.
Co-reporter:Dr. Colan E. Hughes;P. Andrew Williams ; Kenneth D. M. Harris
Angewandte Chemie International Edition 2014 Volume 53( Issue 34) pp:8939-8943
Publication Date(Web):
DOI:10.1002/anie.201404266
Abstract
A new in-situ NMR strategy (termed CLASSIC NMR) for mapping the evolution of crystallization processes is reported, involving simultaneous measurement of both liquid-state and solid-state NMR spectra as a function of time. This combined strategy allows complementary information to be obtained on the evolution of both the solid and liquid phases during the crystallization process. In particular, as crystallization proceeds (monitored by solid-state NMR), the solution state becomes more dilute, leading to changes in solution-state speciation and the modes of molecular aggregation in solution, which are monitored by liquid-state NMR. The CLASSIC NMR experiment is applied here to yield new insights into the crystallization of m-aminobenzoic acid.
Co-reporter:Dr. Colan E. Hughes;P. Andrew Williams ; Kenneth D. M. Harris
Angewandte Chemie 2014 Volume 126( Issue 34) pp:9085-9089
Publication Date(Web):
DOI:10.1002/ange.201404266
Abstract
A new in-situ NMR strategy (termed CLASSIC NMR) for mapping the evolution of crystallization processes is reported, involving simultaneous measurement of both liquid-state and solid-state NMR spectra as a function of time. This combined strategy allows complementary information to be obtained on the evolution of both the solid and liquid phases during the crystallization process. In particular, as crystallization proceeds (monitored by solid-state NMR), the solution state becomes more dilute, leading to changes in solution-state speciation and the modes of molecular aggregation in solution, which are monitored by liquid-state NMR. The CLASSIC NMR experiment is applied here to yield new insights into the crystallization of m-aminobenzoic acid.
Co-reporter:Gregory R. Edwards-Gau;Benjamin A. Palmer;Igor P. Dolbnya;Stephen P. Collins;Benson M. Kariuki
Science 2014 Volume 344(Issue 6187) pp:1013-1016
Publication Date(Web):30 May 2014
DOI:10.1126/science.1253537
A close-up view of carbon-bromide bonds
Polarizing filters are widely used in optical microscopy to highlight a range of material properties that cause optical path boundaries or birefringence in a material. Palmer et al. (see the Perspective by Lidin) developed an analog method for x-ray microscopy using linearly polarized x-ray beams and an area detector inside a synchrotron. The technique revealed the orientation of the C-Br bonds within crystalline materials.
Science, this issue p. 1013; see also p. 969
Co-reporter:Benjamin A. Palmer ; Annaïg Le Comte ; Kenneth D.M. Harris ;François Guillaume
Journal of the American Chemical Society 2013 Volume 135(Issue 39) pp:14512-14515
Publication Date(Web):September 4, 2013
DOI:10.1021/ja406866a
We report four experimental strategies for controlling the three-dimensional arrangement of molecules in multicomponent organic crystals, exploiting confocal Raman microspectrometry to quantify the three-dimensional spatial distributions. Specifically, we focus on controlling the distribution of two types of guest molecule in solid organic inclusion compounds to produce composite core–shell crystals, crystals with a homogeneous distribution of the components, crystals with continuous compositional variation from the core to the surface, and crystals with alternating shells of the components. In this context, confocal Raman microspectrometry is particularly advantageous over optical microscopy as it is nondestructive, offers micrometric spatial resolution, and relies only on the component molecules having different vibrational properties.
Co-reporter:Yuncheng Yan, Colan E. Hughes, Benson M. Kariuki, and Kenneth D. M. Harris
Crystal Growth & Design 2013 Volume 13(Issue 1) pp:27-30
Publication Date(Web):December 5, 2012
DOI:10.1021/cg3016035
We report polymorphism in a co-crystal system comprising trimesic acid (benzene-1,3,5-tricarboxylic acid, TMA), tert-butylamine (TBA), and methanol with stoichiometry (TMA)2(TBA)5(methanol)3. The crystal structure of each polymorph (determined from single-crystal X-ray diffraction) is shown to have 10 independent molecules in the asymmetric unit. In each polymorph, all five TBA molecules in the asymmetric unit exist as protonated cations, whereas, of the two TMA molecules in the asymmetric unit, one exists as the doubly deprotonated anion and the other exists as the triply deprotonated anion. In each case, the structure is based on an extensively hydrogen-bonded two-dimensional network involving the −N+H3 groups of TBA cations, the −CO2– and −CO2H groups of TMA anions, and the OH groups of methanol molecules. Although the two polymorphs share some structural features in common, there are nevertheless significant differences in several aspects, including differences in some of the hydrogen-bonding motifs. Among polymorphic systems reported previously, there are very few examples for which two polymorphs have 10 or more independent molecules in the asymmetric unit and very few examples of co-crystals comprising three or more distinct organic molecules. From both of these perspectives, the example of polymorphism reported here can be considered very rare.
Co-reporter:Dr. Javier Martí-Rujas;Dr. Lorenzo Meazza;Dr. Gin Keat Lim;Dr. Giancarlo Terraneo;Dr. Tullio Pilati;Dr. Kenneth D. M. Harris;Dr. Pierangelo Metrangolo;Dr. Giuseppe Resnati
Angewandte Chemie International Edition 2013 Volume 52( Issue 50) pp:
Publication Date(Web):
DOI:10.1002/anie.201309857
Co-reporter:Dr. Javier Martí-Rujas;Dr. Lorenzo Meazza;Dr. Gin Keat Lim;Dr. Giancarlo Terraneo;Dr. Tullio Pilati;Dr. Kenneth D. M. Harris;Dr. Pierangelo Metrangolo;Dr. Giuseppe Resnati
Angewandte Chemie International Edition 2013 Volume 52( Issue 50) pp:13444-13448
Publication Date(Web):
DOI:10.1002/anie.201307552
Co-reporter:Dr. Javier Martí-Rujas;Dr. Lorenzo Meazza;Dr. Gin Keat Lim;Dr. Giancarlo Terraneo;Dr. Tullio Pilati;Dr. Kenneth D. M. Harris;Dr. Pierangelo Metrangolo;Dr. Giuseppe Resnati
Angewandte Chemie 2013 Volume 125( Issue 50) pp:
Publication Date(Web):
DOI:10.1002/ange.201309857
Co-reporter:Dr. Javier Martí-Rujas;Dr. Lorenzo Meazza;Dr. Gin Keat Lim;Dr. Giancarlo Terraneo;Dr. Tullio Pilati;Dr. Kenneth D. M. Harris;Dr. Pierangelo Metrangolo;Dr. Giuseppe Resnati
Angewandte Chemie 2013 Volume 125( Issue 50) pp:13686-13690
Publication Date(Web):
DOI:10.1002/ange.201307552
Co-reporter:Dmytro V. Dudenko, P. Andrew Williams, Colan E. Hughes, Oleg N. Antzutkin, Sitaram P. Velaga, Steven P. Brown, and Kenneth D. M. Harris
The Journal of Physical Chemistry C 2013 Volume 117(Issue 23) pp:12258-12265
Publication Date(Web):May 3, 2013
DOI:10.1021/jp4041106
We report a strategy for structure determination of organic materials in which complete solid-state nuclear magnetic resonance (NMR) spectral data is utilized within the context of structure determination from powder X-ray diffraction (XRD) data. Following determination of the crystal structure from powder XRD data, first-principles density functional theory-based techniques within the GIPAW approach are exploited to calculate the solid-state NMR data for the structure, followed by careful scrutiny of the agreement with experimental solid-state NMR data. The successful application of this approach is demonstrated by structure determination of the 1:1 cocrystal of indomethacin and nicotinamide. The 1H and 13C chemical shifts calculated for the crystal structure determined from the powder XRD data are in excellent agreement with those measured experimentally, notably including the two-dimensional correlation of 1H and 13C chemical shifts for directly bonded 13C–1H moieties. The key feature of this combined approach is that the quality of the structure determined is assessed both against experimental powder XRD data and against experimental solid-state NMR data, thus providing a very robust validation of the veracity of the structure.
Co-reporter:P. Andrew Williams, Colan. E. Hughes, Asma B. M. Buanz, Simon Gaisford, and Kenneth D. M. Harris
The Journal of Physical Chemistry C 2013 Volume 117(Issue 23) pp:12136-12145
Publication Date(Web):May 3, 2013
DOI:10.1021/jp401547f
To date, only one crystal structure of l-phenylalanine has been reported, with no confirmed report of polymorphism of this material. In the present work, we report the discovery of a new polymorph of l-phenylalanine, with the structural properties determined directly from powder X-ray diffraction data. The new polymorph of l-phenylalanine is stable only under rigorously dry conditions. In addition, two new solid hydrate phases of l-phenylalanine have been discovered: a monohydrate and a hemihydrate. The hemihydrate is susceptible to partial water deficiency. The crystal structures of the monohydrate and hemihydrate phases have also been determined directly from powder X-ray diffraction data. On the basis of results from dynamic vapor sorption and other experiments, we demonstrate that the three new solid forms are readily interconvertible as a function of relative humidity.
Co-reporter:Emilie Courvoisier, P. Andrew Williams, Gin Keat Lim, Colan E. Hughes and Kenneth D. M. Harris
Chemical Communications 2012 vol. 48(Issue 22) pp:2761-2763
Publication Date(Web):12 Jan 2012
DOI:10.1039/C2CC17203H
We report the crystal structure of L-arginine, one of the last remaining natural amino acids for which the crystal structure has never been determined; structure determination was carried out directly from powder X-ray diffraction (XRD) data, exploiting the direct-space genetic algorithm technique for structure solution followed by Rietveld refinement.
Co-reporter:James A. Platts, Hasmerya Maarof, Kenneth D. M. Harris, Gin Keat Lim and David J. Willock
Physical Chemistry Chemical Physics 2012 vol. 14(Issue 34) pp:11944-11952
Publication Date(Web):12 Jul 2012
DOI:10.1039/C2CP41716B
Ab initio and density functional theory (DFT) calculations on some model systems are presented to assess the extent to which intermolecular hydrogen bonding can affect the planarity of amide groups. Formamide and urea are examined as archetypes of planar and non-planar amides, respectively. DFT optimisations suggest that appropriately disposed hydrogen-bond donor or acceptor molecules can induce non-planarity in formamide, with OCNH dihedral angles deviating by up to ca. 20° from planarity. Ab initio energy calculations demonstrate that the energy required to deform an amide molecule from the preferred geometry of the isolated molecule is more than compensated by the stabilisation due to hydrogen bonding. Similarly, the NH2 group in urea can be made effectively planar by the presence of appropriately positioned hydrogen-bond acceptors, whereas hydrogen-bond donors increase the non-planarity of the NH2 group. Small clusters (a dimer, two trimers and a pentamer) extracted from the crystal structure of urea indicate that the crystal field acts to force planarity of the urea molecule; however, the interaction with nearest neighbours alone is insufficient to induce the molecule to become completely planar, and longer-range effects are required. Finally, the potential for intermolecular hydrogen bonding to induce non-planarity in a model of a peptide is explored. Inter alia, the insights obtained in the present work on the extent to which the geometry of amide groups may be deformed under the influence of intermolecular hydrogen bonding provide structural guidelines that can assist the interpretation of the geometries of such groups in structure determination from powder X-ray diffraction data.
Co-reporter:Benjamin A. Palmer, Benson M. Kariuki, Anabel Morte-Ródenas, and Kenneth D. M. Harris
Crystal Growth & Design 2012 Volume 12(Issue 2) pp:577-582
Publication Date(Web):January 10, 2012
DOI:10.1021/cg201656y
Structural properties of the bromocyclohexane/thiourea inclusion compound have been determined using both single-crystal and powder X-ray diffraction over a range of temperatures above and below a first-order phase transition at 233 K in this material. The results demonstrate marked contrasts to the phase transition behavior in the prototypical cyclohexane/thiourea inclusion compound, demonstrating that relatively small changes in molecular geometry (in this case bromine substitution) can have a profound influence on the structural properties of the low-temperature phase in such materials.
Co-reporter:Xiaohe Ma, Gin Keat Lim, Kenneth D. M. Harris, David C. Apperley, Peter N. Horton, Michael B. Hursthouse, and Stuart L. James
Crystal Growth & Design 2012 Volume 12(Issue 12) pp:5869-5872
Publication Date(Web):October 24, 2012
DOI:10.1021/cg301291w
The aluminum complex Alq3 (q = 8-hydroxyquinolinate), which has important applications in organic light-emitting diode materials, is shown to be readily synthesized as a pure phase under solvent-free mechanochemical conditions from Al(OAc)2OH and 8-hydroxyquinoline by ball milling. The initial product of the mechanochemical synthesis is a novel acetic acid solvate of Alq3, and the α polymorph of Alq3 is obtained on subsequent heating/desolvation of this phase. The structure of the mechanochemically prepared acetic acid solvate of Alq3 has been determined directly from powder X-ray diffraction data and is shown to be a different polymorph from the corresponding acetic acid solvate prepared by solution-state crystallization of Alq3 from acetic acid. Significantly, the mechanochemical synthesis of Alq3 is shown to be fully scalable across two orders of magnitude from 0.5 to 50 g scale. The Alq3 sample obtained from the solvent-free mechanochemical synthesis is analytically pure and exhibits identical photoluminescence behavior to that of a sample prepared by the conventional synthetic route.
Co-reporter:P. Andrew Williams, Colan E. Hughes, and Kenneth D. M. Harris
Crystal Growth & Design 2012 Volume 12(Issue 12) pp:5839-5845
Publication Date(Web):November 6, 2012
DOI:10.1021/cg300599q
Recently, a second crystalline polymorph (Form II) of racemic ibuprofen was reported to be obtained by crystallization from the supercooled liquid state. The reported procedure involved a temperature schedule that included the requirement to quench the sample to a temperature (168 K) significantly below the glass-transition temperature (228 K) followed by annealing at a temperature (typically 258 K) above the glass-transition temperature. In the present work, we show (by differential scanning calorimetry and in situ, variable-temperature powder X-ray diffraction) that Form II of racemic ibuprofen can be prepared by crystallization from the supercooled liquid at temperatures as high as 273 K, without the requirement for low-temperature quenching and without the requirement for the material to pass below the glass-transition temperature. Our results lead to a new interpretation of the experimental conditions for producing Form II of racemic ibuprofen and remove racemic ibuprofen from the set of crystalline materials that are obtained only via low-temperature quenching of a supercooled liquid.
Co-reporter:P. Andrew Williams, Colan E. Hughes, Gin Keat Lim, Benson M. Kariuki, and Kenneth D. M. Harris
Crystal Growth & Design 2012 Volume 12(Issue 6) pp:3104-3113
Publication Date(Web):April 10, 2012
DOI:10.1021/cg3003178
Given the importance of the phenomenon of polymorphism from both fundamental and applied perspectives, there is considerable interest in the discovery of new systems that exhibit abundant polymorphism. In the present article, the preparation strategies and structural properties of three new polymorphs (denoted Forms III, IV, and V) of m-aminobenzoic acid (m-ABA) are reported, elevating this system to the rare class of polymorphic systems with at least five known polymorphs. The crystal structures of the three new polymorphs have been determined directly from powder X-ray diffraction data, using the direct-space genetic algorithm technique for structure solution followed by Rietveld refinement, demonstrating the opportunities that now exist for determining crystal structures when crystals of sufficient size and quality for single-crystal X-ray diffraction are not available. In two of the new polymorphs (Forms III and IV), the m-ABA molecules exist in the zwitterionic form (as in the previously known Form I), while the m-ABA molecules in the other new polymorph (Form V) are nonzwitterionic (as in the previously known Form II). Furthermore, disorder of the molecular orientation, and hence disorder in the intermolecular hydrogen-bonding arrangement, is revealed in Form V. The assignment of the tautomeric form in each polymorph is confirmed by X-ray photoelectron spectroscopy. Issues relating to the relative stabilities of the five polymorphs of m-ABA are discussed.
Co-reporter:Benjamin A. Palmer, Gregory R. Edwards-Gau, Anabel Morte-Ródenas, Benson M. Kariuki, Gin Keat Lim, Kenneth D.M. Harris, Igor P. Dolbnya, and Stephen P. Collins
The Journal of Physical Chemistry Letters 2012 Volume 3(Issue 21) pp:3216-3222
Publication Date(Web):October 10, 2012
DOI:10.1021/jz3013547
While the phenomenon of birefringence is well-established in the case of visible radiation and is exploited in many fields (e.g., through the use of the polarizing optical microscope), the analogous phenomenon for X-rays has been a virtually neglected topic. Here, we demonstrate the scope and potential for exploiting X-ray birefringence to determine the orientational properties of specific types of bonds in solids. Specifically, orientational characteristics of C–Br bonds in the bromocyclohexane/thiourea inclusion compound are elucidated from X-ray birefringence measurements at energies close to the bromine K-edge, revealing inter alia the changes in the orientational distribution of the C–Br bonds associated with a low-temperature order–disorder phase transition. From fitting a theoretical model to the experimental data, reliable quantitative information on the orientational properties of the C–Br bonds is determined. The experimental strategy reported here represents the basis of a new approach for gaining insights into the orientational properties of molecules in anisotropic materials.Keywords: molecular orientation; phase transition; solid inclusion compound; synchrotron; X-ray birefringence;
Co-reporter:Colan E. Hughes, P. Andrew Williams, Thomas R. Peskett, and Kenneth D. M. Harris
The Journal of Physical Chemistry Letters 2012 Volume 3(Issue 21) pp:3176-3181
Publication Date(Web):October 12, 2012
DOI:10.1021/jz301252u
We report the discovery of new polymorphic forms of solids by exploiting a solid-state NMR technique that has been developed for in situ monitoring of the evolution of crystallization processes. The capability of the technique to reveal the existence of new polymorphic forms of molecular solids is illustrated by the discovery of two new polymorphs of methyldiphenylphosphine oxide and a new solid form of the 1,10-dihydroxydecane/urea system.Keywords: crystallization; in situ techniques; polymorphism; solid-state NMR;
Co-reporter:Benjamin A. Palmer, Benson M. Kariuki, Vamsee K. Muppidi, Colan E. Hughes and Kenneth D. M. Harris
Chemical Communications 2011 vol. 47(Issue 13) pp:3760-3762
Publication Date(Web):03 Feb 2011
DOI:10.1039/C0CC05477A
X-Ray diffraction studies reveal that the tunnel inclusion compound formed between 1-tert-butyl-4-iodobenzene and thiourea has an incommensurate relationship between the periodicities of the host and guest substructures along the tunnel axis, representing the first reported case of an incommensurate thiourea inclusion compound.
Co-reporter:Rafel Prohens, Anna Portell, Cristina Puigjaner, Salvador Tomàs, Kotaro Fujii, Kenneth D. M. Harris, Xavier Alcobé, Mercè Font-Bardia, and Rafael Barbas
Crystal Growth & Design 2011 Volume 11(Issue 9) pp:3725-3730
Publication Date(Web):August 4, 2011
DOI:10.1021/cg200772e
Using a dipyridyl squaramide derivative as a model, we have shown that cooperativity in hydrogen-bonded catemers plays a crucial role in defining the solid-state synthon of disecondary squaramides, overriding the preferred association mode in solution.
Co-reporter:Eugene Y. Cheung, Kotaro Fujii, Fang Guo, Kenneth D. M. Harris, Sayoko Hasebe, and Reiko Kuroda
Crystal Growth & Design 2011 Volume 11(Issue 8) pp:3313
Publication Date(Web):June 3, 2011
DOI:10.1021/cg200379h
A new anhydrous chiral phase of Ru(bipy)3(ClO4)2 (bipy = 2,2′-bipyridine) has been prepared both by mechanical grinding followed by annealing of the known chiral hydrate phase of this material and by solid-state dehydration of the chiral hydrate phase at high temperature. The new phase is obtained from these processes as a microcrystalline powder, thus limiting the opportunity to carry out structural characterization by single-crystal X-ray diffraction. Instead, our structure determination of the new chiral anhydrous phase has exploited the capabilities of modern powder X-ray diffraction techniques, employing the direct-space genetic algorithm technique for structure solution followed by Rietveld refinement. The structural properties of the chiral anhydrous phase are discussed, particularly with regard to assessing the structural relationship to the parent hydrate phase.
Co-reporter:Gin Keat Lim, Kotaro Fujii, Kenneth D. M. Harris, and David C. Apperley
Crystal Growth & Design 2011 Volume 11(Issue 12) pp:5192-5199
Publication Date(Web):October 13, 2011
DOI:10.1021/cg201230k
The structural properties of a new polymorph of a material distributed commercially as “hexaketocyclohexane octahydrate” have been determined directly from powder X-ray diffraction data, employing the direct-space genetic algorithm technique for structure solution followed by Rietveld refinement. It is shown that the molecule actually present in the crystal structure is dodecahydroxycyclohexane (C6(OH)12) rather than hexaketocyclohexane (C6O6). This assignment is also confirmed from high-resolution solid-state 13C NMR data. The crystal structure contains two molecules of water per molecule of C6(OH)12. In the asymmetric unit, there are 16 hydrogen-bond donor groups (O–H bonds) and 14 hydrogen-bond acceptors (oxygen atoms), leading to multiple permutations for intermolecular hydrogen-bonding arrangements. Detailed analysis of the results from Rietveld refinement suggests that a disordered model provides the most appropriate description of the hydrogen-bonding arrangement, in which the hydrogen atom of each OH group of C6(OH)12 and the hydrogen atoms of each water molecule are distributed among several different intermolecular O–H···O hydrogen bonds. The density of this material (1.926 g cm–3 at ambient temperature) is one of the highest ever reported densities among organic materials that contain no elements heavier than oxygen.
Co-reporter:Javier Martí-Rujas, Benson M. Kariuki, Colan E. Hughes, Anabel Morte-Ródenas, Fang Guo, Zornitza Glavcheva-Laleva, Kemal Taştemür, Li-ling Ooi, Lily Yeo and Kenneth D. M. Harris
New Journal of Chemistry 2011 vol. 35(Issue 7) pp:1515-1521
Publication Date(Web):11 May 2011
DOI:10.1039/C1NJ20040B
A family of stoichiometric (2:1 molar ratio) co-crystals formed between urea and α,ω-dihydroxyalkanes of even chain length [HO(CH2)nOH, n = 2m, m = 3–8] is shown to exhibit three well-defined structure types, which are rationalized on the basis of specific hydrogen-bonding motifs. In spite of the structural diversity observed for different α,ω-dihydroxyalkane chain lengths, there is no evidence that any member of this family of co-crystals exhibits polymorphism (i.e. none of the α,ω-dihydroxyalkane/urea systems is observed to exist in more than one of the well-defined co-crystal structure types).
Co-reporter:Benjamin A. Palmer, Anabel Morte-Ródenas, Benson M. Kariuki, Kenneth D. M. Harris, and Stephen P. Collins
The Journal of Physical Chemistry Letters 2011 Volume 2(Issue 18) pp:2346-2351
Publication Date(Web):August 25, 2011
DOI:10.1021/jz201026z
Whereas the phenomenon of birefringence is well-established and widely applied in the case of linearly polarized visible light (for example, underpinning the use of the polarizing optical microscope), the study of birefringence using linearly polarized X-rays is an essentially unexplored field. To address this issue, we report a material that exhibits ideal birefringence behavior at X-ray energies near the Br K-edge. The designed material, the 1-bromoadamantane/thiourea inclusion compound, gives experimental behavior in excellent agreement with theoretical predictions for the dependence of transmitted X-ray intensity on both X-ray energy and crystal orientation. Our results vindicate the potential to exploit X-ray birefringence to establish a detailed understanding of molecular polarization, particularly as an experimental strategy to determine the orientational distributions of specific bonds in solids, for example, in the case of partially ordered materials or materials that undergo order–disorder phase transitions.Keywords: host−guest materials; solid inclusion compounds; synchrotron radiation; X-ray birefringence; X-ray dichroism; X-ray optics;
Co-reporter:Andrew J. Ilott, Sebastian Palucha, Andrei S. Batsanov, Kenneth D. M. Harris, Paul Hodgkinson, and Mark R. Wilson
The Journal of Physical Chemistry B 2011 Volume 115(Issue 12) pp:2791-2800
Publication Date(Web):March 10, 2011
DOI:10.1021/jp110137h
Large-scale molecular dynamics simulations have been performed on solid inclusion compounds formed between urea and alkane (dodecane) and alkanoic acid (dodecanoic acid) guest molecules. The incommensurate nature of the guest and host substructures means that simulations of these systems are challenging, and our results call into question some of the simplifying assumptions made in earlier simulations on the urea inclusion compounds. Detailed information is obtained on the structural properties of the carboxylic acid dimers and alkyl chains confined within the nanoscale tunnels of the urea host structure, including the chirality of the guest conformation induced by the chiral nature of the urea tunnels. Diffusion coefficients (at 300 K) of the guest molecules along the tunnel axis were determined to be 0.091 ± 0.031 (dodecane) and 0.0063 ± 0.0013 Å2 ps−1 (dodecanoic acid), in good agreement with experimental measurements on alkane/urea systems. Weak ordering is observed between guests in neighboring tunnels, which is compatible with experimental measurements on the alkane/urea systems, although the simulations provide more detailed molecular-level insights into the nature of this supramolecular ordering.
Co-reporter:Abil E. Aliev, Sam E. Mann, Aisha S. Rahman, Paul F. McMillan, Furio Corà, Dinu Iuga, Colan E. Hughes, and Kenneth D. M. Harris
The Journal of Physical Chemistry A 2011 Volume 115(Issue 44) pp:12201-12211
Publication Date(Web):September 22, 2011
DOI:10.1021/jp207592u
High-resolution solid-state 2H MAS NMR studies of the α and γ polymorphs of fully deuterated glycine (glycine-d5) are reported. Analysis of spinning sideband patterns is used to determine the 2H quadrupole interaction parameters, and is shown to yield good agreement with the corresponding parameters determined from single-crystal 2H NMR measurements (the maximum deviation in quadrupole coupling constants determined from these two approaches is only 1%). From analysis of simulated 2H MAS NMR sideband patterns as a function of reorientational jump frequency (κ) for the −N+D3 group in glycine-d5, the experimentally observed differences in the 2H MAS NMR spectrum for the −N+D3 deutrons in the α and γ polymorphs is attributed to differences in the rate of reorientation of the −N+D3 group. These simulations show severe broadening of the 2H MAS NMR signal in the intermediate motion regime, suggesting that deuterons undergoing reorientational motions at rates in the range κ ≈ 104–106 s–1 are likely to be undetectable in 2H MAS NMR measurements for materials with natural isotopic abundances. The 1H NMR chemical shifts for the α and γ polymorphs of glycine have been determined from the 2H MAS NMR results, taking into account the known second-order shift. Further quantum mechanical calculations of 2H quadrupole interaction parameters and 1H chemical shifts reveal the structural dependence of these parameters in the two polymorphs and suggest that the existence of two short intermolecular C–H···O contacts for one of the H atoms of the >CH2 group in the α polymorph have a significant influence on the 2H quadrupole coupling and 1H chemical shift for this site.
Co-reporter:Abil E. Aliev, Sam E. Mann, Dinu Iuga, Colan E. Hughes, and Kenneth D. M. Harris
The Journal of Physical Chemistry A 2011 Volume 115(Issue 22) pp:5568-5578
Publication Date(Web):May 12, 2011
DOI:10.1021/jp202810k
High-resolution solid-state 2H NMR spectroscopy provides a method for measuring 1H NMR chemical shifts in solids and is advantageous over the direct measurement of high-resolution solid-state 1H NMR spectra, as it requires only the application of routine magic angle sample spinning (MAS) and routine 1H decoupling methods, in contrast to the requirement for complex pulse sequences for homonuclear 1H decoupling and ultrafast MAS in the case of high-resolution solid-state 1H NMR. However, a significant obstacle to the routine application of high-resolution solid-state 2H NMR is the very low natural abundance of 2H, with the consequent problem of inherently low sensitivity. Here, we explore the feasibility of measuring 2H MAS NMR spectra of various solids with natural isotopic abundances at high magnetic field (850 MHz), focusing on samples of amino acids, peptides, collagen, and various organic solids. The results show that high-resolution solid-state 2H NMR can be used successfully to measure isotropic 1H chemical shifts in favorable cases, particularly for mobile functional groups, such as methyl and −N+H3 groups, and in some cases phenyl groups. Furthermore, we demonstrate that routine 2H MAS NMR measurements can be exploited for assessing the relative dynamics of different functional groups in a molecule and for assessing whole-molecule motions in the solid state. The magnitude and field-dependence of second-order shifts due to the 2H quadrupole interaction are also investigated, on the basis of analysis of simulated and experimental 1H and 2H MAS NMR spectra of fully deuterated and selectively deuterated samples of the α polymorph of glycine at two different magnetic field strengths.
Co-reporter:Colan E. Hughes and Kenneth D. M. Harris
Chemical Communications 2010 vol. 46(Issue 27) pp:4982-4984
Publication Date(Web):27 May 2010
DOI:10.1039/C0CC01007C
Application of a technique developed for in situ solid-state 13C NMR studies of crystallization processes reveals direct evidence that crystallization of glycine from a methanol/water solution involves the initial transient formation of the β polymorph, which then undergoes a solution-mediated polymorphic transformation to yield the more stable α polymorph.
Co-reporter:Kotaro Fujii, Yasunari Ashida, Hidehiro Uekusa, Fang Guo and Kenneth D. M. Harris
Chemical Communications 2010 vol. 46(Issue 24) pp:4264-4266
Publication Date(Web):12 May 2010
DOI:10.1039/C0CC00233J
The methanol solvate crystalline phase (M) of benzene-1,2,4,5-tetracarboxylic acid transforms selectively to a hydrate phase (H) or a non-solvate phase (N) depending on the presence of atmospheric water vapour; knowledge of the crystal structures of M and N, determined here using single-crystal and powder X-ray diffraction, respectively, yields insights into mechanistic aspects of the solid-state transformations.
Co-reporter:Kotaro Fujii, Ana Lazuen Garay, Janeen Hill, Elena Sbircea, Zhigang Pan, Mingcan Xu, David C. Apperley, Stuart L. James and Kenneth D. M. Harris
Chemical Communications 2010 vol. 46(Issue 40) pp:7572-7574
Publication Date(Web):17 Sep 2010
DOI:10.1039/C0CC02635B
Powder X-ray diffraction (XRD) has been exploited to establish the structural properties of a porous interpenetrated mixed-ligand metal–organic framework material prepared by solid-state grinding, recognizing that product phases from mechanochemical synthesis are typically microcrystalline powders. The importance of subjecting the powder XRD data to rigorous scrutiny in such applications is emphasized.
Co-reporter:Javier Martí-Rujas, Anabel Morte-Ródenas, Fang Guo, Nigel Thomas, Kotaro Fujii, Benson M. Kariuki and Kenneth D. M. Harris
Crystal Growth & Design 2010 Volume 10(Issue 7) pp:3176
Publication Date(Web):May 27, 2010
DOI:10.1021/cg100330c
Solid tert-butylammonium acetate monohydrate undergoes a facile solid-state dehydration process under ambient conditions, in which single crystals of the monohydrate phase transform to a microcrystalline powder of an anhydrous product phase. The structural properties of the anhydrous phase have been determined directly from powder X-ray diffraction data, employing the direct-space genetic algorithm technique for structure solution followed by Rietveld refinement, allowing rationalization of the structural changes associated with the dehydration process. The dehydration process is associated with substantial reorganization of the hydrogen bonding arrangement, although one component of the hydrogen-bonding scheme is actually preserved in the transformation.
Co-reporter:Gin Keat Lim, Zhongfu Zhou, Kotaro Fujii, Patrizia Calcagno, Emilio Tedesco, Simon J. Kitchin, Benson M. Kariuki, Douglas Philp and Kenneth D. M. Harris
Crystal Growth & Design 2010 Volume 10(Issue 8) pp:3814
Publication Date(Web):July 12, 2010
DOI:10.1021/cg100715v
Rationalization of the solid-state structural properties of odd members (n = 3, 5, 7) of the series Ph2P(O)(CH2)nP(O)Ph2 leads to insights concerning the structural determinants of this class of material, particularly with regard to the formation of preferred arrangements of P═O dipoles. The odd members of this series are recalcitrant to the formation of single crystals of suitable size and quality for single-crystal X-ray diffraction, and modern techniques for carrying out crystal structure determination directly from powder X-ray diffraction data were essential for determining the structural properties of these materials. In the present work, nonsolvate crystal phases of the materials with n = 3 and 5 were prepared by appropriate solid-state desolvation processes (starting from hydrate and toluene solvate phases, respectively), yielding microcrystalline powders of the nonsolvate phase in each case. Structure determination was carried out directly from powder X-ray diffraction data, employing the direct-space genetic algorithm technique for structure solution followed by Rietveld refinement.
Co-reporter:Kotaro Fujii, Hidehiro Uekusa, Naoko Itoda, Gen Hasegawa, Etsuo Yonemochi, Katsuhide Terada, Zhigang Pan and Kenneth D. M. Harris
The Journal of Physical Chemistry C 2010 Volume 114(Issue 1) pp:580-586
Publication Date(Web):November 17, 2009
DOI:10.1021/jp908636t
The extensively used antibacterial agent acrinol is known to form a monohydrate phase (H) on crystallization from water. We demonstrate here that acrinol also forms two anhydrous polymorphs, denoted form I (AI) and form II (AII). Polymorph AI is obtained directly on heating H, by a solid-state dehydration process, and polymorph AII is obtained subsequently from AI, by a polymorphic transformation. The crystal structures of AI and AII have been determined directly from powder X-ray diffraction data, employing the direct-space genetic algorithm technique for structure solution, followed by Rietveld refinement. From the structural properties of AI and AII, mechanistic aspects of the dehydration process and the polymorphic transformation have been established. From measurements of initial dissolution rates and enthalpies of dissolution, AII is assigned as the thermodynamically stable polymorph, with a monotropic relationship between AI and AII. The hydration properties of AI and AII differ significantly, with hydration of AI occurring at substantially lower relative humidity than AII.
Co-reporter:BenjaminA. Palmer;KennethD.M. Harris Dr.;François Guillaume Dr.
Angewandte Chemie International Edition 2010 Volume 49( Issue 30) pp:5096-5100
Publication Date(Web):
DOI:10.1002/anie.201000952
Co-reporter:BenjaminA. Palmer;KennethD.M. Harris Dr.;François Guillaume Dr.
Angewandte Chemie 2010 Volume 122( Issue 30) pp:5222-5226
Publication Date(Web):
DOI:10.1002/ange.201000952
Co-reporter:Shanshan Huang, Kenneth D. M. Harris, Elisa Lopez-Capel, David A. C. Manning and David Rickard
Inorganic Chemistry 2009 Volume 48(Issue 24) pp:11486-11488
Publication Date(Web):November 17, 2009
DOI:10.1021/ic901512z
The application of a range of experimental techniques shows that “amorphous nickel sulfide” (the material precipitated from aqueous solutions of NiII salts and SII− under ambient conditions) is actually a hydrated nanoparticulate material with an approximate formula NiS·1.5H2O. The particles comprise a crystalline, anhydrous core (diameter ca. 1−3 nm) with the millerite (NiS) structure, surrounded by a hydrated shell phase. The materials prepared under acidic conditions (pH = 3 and 5) transform with age to form polydymite (Ni3S4) and heazlewoodite (Ni3S2), while materials prepared at pH = 7 and 9 do not undergo this transformation. At pH = 12, the preparation procedure yields NiAs-type NiS as a metastable phase.
Co-reporter:Massimo Mella and Kenneth D. M. Harris
Physical Chemistry Chemical Physics 2009 vol. 11(Issue 47) pp:11340-11346
Publication Date(Web):27 Oct 2009
DOI:10.1039/B911556K
Computational techniques (second order Møller–Plesset MP2 perturbation theory in conjunction with medium and large size basis sets) are applied to explore structural aspects of a hydrogen-bonded tetrameric cluster of methanol molecules, based geometrically on a tetrahedral arrangement of the four oxygen atoms of the cluster. The hydrogen-bonded structures that represent minima on the potential energy surface are established, and the complete set of pathways that allow interconversion between these structures through “switching” of the hydrogen bonding arrangement are elucidated. The implications of these results in terms of dynamic properties of the cluster are discussed.
Co-reporter:Kotaro Fujii, Yasunari Ashida, Hidehiro Uekusa, Shinya Hirano, Shinji Toyota, Fumio Toda, Zhigang Pan and Kenneth D. M. Harris
Crystal Growth & Design 2009 Volume 9(Issue 2) pp:1201
Publication Date(Web):December 22, 2008
DOI:10.1021/cg801142p
A new co-crystal (phase H) of 5-methyl-2-pyridone (5MP) and trimesic acid (TMA) has been prepared by grinding a methanol solvate co-crystal (phase M) of 5MP and TMA under ambient conditions. Powder X-ray diffraction indicates that the new co-crystal phase H is structurally different from the methanol solvate co-crystal (phase M) and an unsolvated co-crystal (phase U) of 5MP and TMA reported previously. In the present work, the crystal structure of the new phase H has been determined directly from powder X-ray diffraction data, allowing insights to be gained regarding the mechanism of the transformation from M to H. The structural analysis reveals that phase H is a hydrate of 5MP and TMA, and thus the transformation from M to H is a solvent exchange process. The rate of this process is shown to be accelerated significantly by grinding. Further vapour induced transformations have been investigated for phases M, H, and U, and insights regarding transformation mechanisms have been established from consideration of the crystal structures.
Co-reporter:Elizabeth J. MacLean, Maryjane Tremayne, Benson M. Kariuki, James R. A. Cameron, Mark A. Roberts and Kenneth D. M. Harris
Crystal Growth & Design 2009 Volume 9(Issue 2) pp:853
Publication Date(Web):January 9, 2009
DOI:10.1021/cg800466x
The latent pigment 1,4-diketo-2,5-di-t-butoxycarbonyl-3,6-diphenylpyrrolo[3,4-c]pyrrole (DPP-Boc) has three well-characterized polymorphic forms (denoted α, β, and γ) in the solid state, although some confusion exists in the literature concerning the assignment of these polymorphs. This paper clarifies the assignment of the three polymorphs of DPP-Boc, discusses various issues concerning the polymorphism of this material, and highlights several general issues regarding the characterization, discovery, and assignment of polymorphic systems.
Co-reporter:Colan E. Hughes and Kenneth D. M. Harris
New Journal of Chemistry 2009 vol. 33(Issue 4) pp:713-716
Publication Date(Web):15 Jan 2009
DOI:10.1039/B819199A
This paper reports the first systematic studies of the effect of deuteration on the polymorphic outcome of the crystallization of glycine from water, focusing on crystallization experiments carried out as a function of the level of deuteration in the system; the dependence of polymorphic outcome on the time of the crystallization process is also explored.
Co-reporter:Mingcan Xu, Kenneth D.M. Harris, John Meurig Thomas
Solid State Nuclear Magnetic Resonance 2009 Volume 35(Issue 2) pp:93-99
Publication Date(Web):April 2009
DOI:10.1016/j.ssnmr.2008.12.011
Hydration of the ammonium form of the solid acid catalyst ZSM-5 is investigated by applying a technique that has been developed recently for carrying out in situ solid-state NMR studies of adsorption processes. From 1H MAS NMR spectra recorded as a function of time and temperature during the hydration process, insights are established on the nature of the interaction between the adsorbed water molecules and the ammonium cations in the ZSM-5 material. The change in isotropic chemical shift for the ammonium cations is consistent with the formation of N–H⋯O hydrogen bonding with the water molecules. Studies of the adsorption of deuterated water, and dehydration of the hydrated material, are also reported.
Co-reporter:Javier Martí-Rujas, Arnaud Desmedt, Kenneth D. M. Harris and François Guillaume
The Journal of Physical Chemistry C 2009 Volume 113(Issue 2) pp:736-743
Publication Date(Web):2017-2-22
DOI:10.1021/jp806380p
Confocal Raman microspectrometry is used to probe, for the first time, the transport of guest molecules along the one-dimensional tunnels in a crystalline urea inclusion compound under conditions of guest exchange in which new guest molecules are introduced simultaneously at both ends of the urea tunnel structure. We focus on the system comprising 1,8-dibromooctane as the original type of guest and pentadecane as the new type of guest, and results are presented for experiments in which the guest exchange process is probed both ex situ and in situ. The Raman data, recorded as a function of position along the tunnel direction and, in the case of the in situ experiments, as a function of time, demonstrate that pentadecane guest molecules enter the tunnels at both ends of the crystal and that transport of guest molecules occurs in both directions along the crystal. Mechanistic aspects of this bidirectional transport process are discussed, particularly in relation to the corresponding process for unidirectional transport of guest molecules in urea inclusion compounds reported previously.
Co-reporter:KennethD.M. Harris ;Sir JohnMeurig Thomas
ChemCatChem 2009 Volume 1( Issue 2) pp:223-231
Publication Date(Web):
DOI:10.1002/cctc.200900181
Abstract
Although the uses of zeolitic materials in heterogeneous catalysis are extensive, the opportunity to develop applications of zeolites in enantioselective catalysis remains underexploited. In part, the relative paucity of chiral zeolite structures is one underlying reason, although some significant progress has been made in recent years in the preparation and structural characterization of chiral zeolitic materials, including the recent report of ITQ-37, the first example of a chiral mesoporous zeolite. However, as elaborated in this Minireview article, the preparation of a chiral zeolite structure is itself not sufficient to ensure that the material will be useful in enantioselective catalysis, and a number of other key issues must also be addressed. In addition to highlighting these issues, this Minireview surveys more widely a number of concepts that are pivotal to the design of chiral solids for the catalysis of enantioselective transformations. In addition to chiral zeolites, a range of other chiral materials, including organic molecular solids, and chiral catalysts, including metal–organic frameworks, chiral metal surfaces, and single-site immobilized organometallic species, are discussed, together with an appraisal of future directions for asymmetric heterogeneous catalysis.
Co-reporter:Mingcan Xu;John Meurig Thomas
Catalysis Letters 2009 Volume 131( Issue 1-2) pp:16-20
Publication Date(Web):2009 August
DOI:10.1007/s10562-009-0031-y
Hydration of the ammonium form of the solid acid catalyst ZSM-5 is investigated by applying a technique developed recently for in situ solid-state NMR studies of adsorption processes. From high-resolution solid-state 1H NMR spectra recorded as a function of time during the hydration process, insights are established concerning the nature of the interaction between the adsorbed water molecules and the ammonium cations in the ZSM-5 host material. In particular, quantitative information is established regarding the clustering of water molecules during the hydration process, and indicates the preferential formation of clusters comprising two water molecules associated with each hydrated ammonium cation.
Co-reporter:Mingcan Xu and Kenneth D. M. Harris
Crystal Growth & Design 2008 Volume 8(Issue 1) pp:6
Publication Date(Web):January 2, 2008
DOI:10.1021/cg701077p
Triple-quantum 23Na MAS NMR spectroscopy has been applied to characterize the three polymorphs of sodium acetate. The crystallographically distinct sodium sites in each of these polymorphs are uniquely identified from the triple-quantum 23Na MAS NMR spectra. These data provide access to the 23Na quadrupole interaction parameters (quadrupole coupling constant and asymmetry parameter) for each sodium site, which provide a quantitative measure of the local structural properties of the sodium cations in each polymorphic form.
Co-reporter:David Albesa-Jové, Zhigang Pan, Kenneth D. M. Harris and Hidehiro Uekusa
Crystal Growth & Design 2008 Volume 8(Issue 10) pp:3641-3645
Publication Date(Web):August 28, 2008
DOI:10.1021/cg800226e
The anhydrous crystalline phase of chloroquine bis-(dihydrogen phosphate) is obtained by dehydration of the corresponding hydrate phase, but in common with many solid-state dehydration processes, the product is obtained as a polycrystalline powder, thus limiting the opportunity to carry out structural characterization using single crystal X-ray diffraction techniques. Instead, structure determination of the anhydrous phase has exploited the capabilities of modern powder X-ray diffraction techniques, employing the direct-space Genetic Algorithm technique for structure solution followed by Rietveld refinement. The results reveal that the dehydration process is associated with a significant change in the topology of hydrogen bonded chains of dihydrogen phosphate anions, arising from a change in the hydrogen bonding arrangement within the chains, together with a significant change in the conformation of the chloroquine cation.
Co-reporter:Zhongfu Zhou and Kenneth D. M. Harris
Physical Chemistry Chemical Physics 2008 vol. 10(Issue 48) pp:7262-7269
Publication Date(Web):31 Oct 2008
DOI:10.1039/B807326K
A new strategy for implementing the concept of a “micro genetic algorithm” within a standard genetic algorithm (GA) procedure is proposed. The strategy operates by applying criteria to test for the occurrence of stagnation within the population of a standard GA calculation, and triggering the micro-GA procedure whenever stagnation is detected. The micro-GA is implemented in terms of the parallel evolution of a number of small sub-populations (comprising predominantly new randomly generated structures together with a few of the best structures from the stagnated population), and the sub-population of highest quality following the micro-GA procedure is used in the construction of the next population of the standard GA calculation. The micro-GA procedure is applied in the context of a GA for carrying out direct-space structure solution from powder X-ray diffraction data, and the results demonstrate that this strategy is an effective means of promoting structural diversity within a stagnated population, leading to significantly improved evolutionary progress. This strategy may prove to be more generally applicable as an approach for alleviating problems due to stagnation in GA calculations in other fields of application.
Co-reporter:Marie Côte ; Colan E. Hughes ; Talbir K. Austin ; Philippe G. A. Rogueda ; Zhigang Pan ; Kenneth D. M. Harris ;Peter C. Griffiths
The Journal of Physical Chemistry C 2008 Volume 112(Issue 37) pp:14570-14578
Publication Date(Web):August 21, 2008
DOI:10.1021/jp800848w
We report several aspects of the characterization of a material (triacetylated-β-cyclodextrin) that exists in two crystalline polymorphic forms (denoted I and II). A striking feature of this polymorphic system is that polymorph I (MPt 194 °C) and polymorph II (MPt 219 °C) exhibit remarkably different solubility in the fluorinated solvent 2H,3H-decafluoropentane, with the solubility higher by a factor of ca. eight for polymorph I at ambient temperature. Structural information established from powder X-ray diffraction and high-resolution solid-state 13C NMR spectroscopy for polymorphs I and II is reported, including crystal structure determination of polymorph II from the powder X-ray diffraction data. Differential scanning calorimetry and high-temperature powder X-ray diffraction demonstrate that the metastable polymorph I converts to the stable polymorph II over a range of elevated temperatures. The combined evidence of these and other techniques suggests that there is a monotropic relationship between polymorphs I and II.
Co-reporter:Said Hamad, Colan E. Hughes, C. Richard A. Catlow and Kenneth D. M. Harris
The Journal of Physical Chemistry B 2008 Volume 112(Issue 24) pp:7280-7288
Publication Date(Web):May 27, 2008
DOI:10.1021/jp711271z
The nature of glycine−glycine interactions in aqueous solution has been studied using molecular dynamics simulations at four different concentrations and, in each case, four different temperatures. Although evidence is found for formation of small, transient hydrogen-bonded clusters of glycine molecules, the main type of interaction between glycine molecules is found to be single N—H···O—C hydrogen bonds. Double-hydrogen-bonded “dimers”, which have often been cited as a significant species present in aqueous solutions of glycine, are only observed infrequently. When double-hydrogen-bonded dimers are formed, they dissociate quickly (typically within less than ca. 4 ps), although the broken hydrogen bonds have a higher than average probability of reforming. Several aspects of the clustering of glycine molecules are investigated as a function of both temperature and concentration, including the size distribution of glycine clusters, the radii of gyration of the clusters, and aspects of the lifetimes of glycine−glycine hydrogen bonding by means of hydrogen-bond correlation functions. Diffusion coefficients for the glycine clusters and water molecules are also investigated and provide results in realistic agreement with experimental results.
Co-reporter:Zhongfu Zhou and Kenneth D. M. Harris
The Journal of Physical Chemistry A 2008 Volume 112(Issue 22) pp:4863-4868
Publication Date(Web):May 8, 2008
DOI:10.1021/jp801185u
There is currently substantial interest and activity in the development and application of a new technique, called “charge flipping” (CF), that has emerged in the past few years for carrying out structure solution from X-ray diffraction data. We report here a new variant of this technique, termed “residue-based charge flipping” (RBCF), in which the residues of calculated and experimental structure factor amplitudes, together with the corresponding electron density residues, are introduced within the CF algorithm. An important feature of this approach is that it does not require a positive threshold electron density value (δ) to be specified to control the charge-flipping step within the algorithm (in contrast, it is well established that the success of standard CF calculations can depend critically on choosing a suitable value of δ for a given structural problem). Methodological details of the RBCF algorithm are described, and the results of the application of this technique for structure solution of three test structures are reported. The RBCF technique is shown to lead to the correct structure solution in all cases, with success rates of at least 90% (for independent calculations from different sets of initial random phases). Significantly, the convergence behavior of RBCF calculations is found to contrast markedly with that generally observed for standard CF calculations. In particular, convergence (assessed from the evolution of R-factor versus iteration number) typically progresses rapidly and immediately from the earliest iterations of RBCF calculations, rather than displaying an extended plateau region. This feature, and the fact that the RBCF technique does not use the δ parameter that is required in standard CF calculations, suggest that the RBCF algorithm may be a promising approach in future applications.
Co-reporter:Colan E. Hughes and Kenneth D. M. Harris
The Journal of Physical Chemistry A 2008 Volume 112(Issue 30) pp:6808-6810
Publication Date(Web):July 9, 2008
DOI:10.1021/jp805182v
We report a technique for carrying out in situ solid-state NMR studies of crystallization from solution, allowing the evolution of different solid state structures (polymorphs) produced during the crystallization process to be identified. The technique exploits selectivity in NMR properties (specifically, the efficiency of cross-polarization from 1H to 13C) between molecules in the solid and solution states, such that the first solid particles produced during the crystallization process are observed selectively, without detecting any signal from dissolved solute (or solvent) molecules. The application of the technique is demonstrated to reveal new insights concerning an isotope effect on the polymorphic outcome of crystallization of glycine from water. As revealed by this example, the in situ solid-state NMR approach reported here creates significant new opportunities for probing and understanding details of the evolution of solid state structures produced during crystallization from solution.
Co-reporter:Eugene Y. Cheung, Sarah E. David, Kenneth D.M. Harris, Barbara R. Conway, Peter Timmins
Journal of Solid State Chemistry 2007 Volume 180(Issue 3) pp:1068-1075
Publication Date(Web):March 2007
DOI:10.1016/j.jssc.2006.12.036
We report the formation and structural properties of co-crystals containing gemfibrozil and hydroxy derivatives of t-butylamine H2NC(CH3)3−n(CH2OH)n, with n=0, 1, 2 and 3. In each case, a 1:1 co-crystal is formed, with transfer of a proton from the carboxylic acid group of gemfibrozil to the amino group of the t-butylamine derivative. All of the co-crystal materials prepared are polycrystalline powders, and do not contain single crystals of suitable size and/or quality for single crystal X-ray diffraction studies. Structure determination of these materials has been carried out directly from powder X-ray diffraction data, using the direct-space Genetic Algorithm technique for structure solution followed by Rietveld refinement. The structural chemistry of this series of co-crystal materials reveals well-defined structural trends within the first three members of the family (n=0, 1, 2), but significantly contrasting structural properties for the member with n=3.Structural properties of a family of co-crystals containing gemfibrozil and hydroxy derivatives of t-butylamine are discussed and rationalized.
Co-reporter:Veronique Siegler Dr.;Eugene Y. Cheung Dr.;Scott Habershon Dr. ;Zhongfu Zhou Dr.;Roy L. Johnston
ChemPhysChem 2007 Volume 8(Issue 5) pp:650-653
Publication Date(Web):9 MAR 2007
DOI:10.1002/cphc.200600726
A successful new strategy to determine the crystal structure from powder diffraction data is based on the genetic algorithm technique for global optimization. Individual molecules are defined as a small number of independent fragments rather than complete molecules (see figure); this increases the success rate, particularly in the challenging case of structure solution of conformationally flexible molecules.
Co-reporter:Mingcan Xu Dr.;David E. W. Vaughan ;John Meurig Thomas Sir
ChemPhysChem 2007 Volume 8(Issue 9) pp:1311-1313
Publication Date(Web):22 MAY 2007
DOI:10.1002/cphc.200700218
A rotor-spinning technique is developed for carrying out in situ studies of adsorption processes by solid-state NMR spectroscopy. The method is suitable for the study of adsorption at the liquid/solid interface, does not require any modification of the NMR instrumentation, and allows spectra to be recorded immediately from the start of the adsorption process (see picture).
Co-reporter:Fang Guo, Meritxell Casadesus, Eugene Y. Cheung, Michael P. Coogan and Kenneth D. M. Harris
Chemical Communications 2006 (Issue 17) pp:1854-1856
Publication Date(Web):21 Mar 2006
DOI:10.1039/B601530A
The product obtained directly from the standard reaction to produce Werner's complex cis-[CoBr(NH3)(en)2]Br2 is shown, via structure determination from powder X-ray diffraction data, to be a racemic crystalline phase; implications of this observation in relation to previous reports that this reaction leads to significant enantiomeric excesses are discussed.
Co-reporter:Simon J. Kitchin, Mingcan Xu, Heliodoro Serrano-González, Laura J. Coates, S. Zaka Ahmed, Christopher Glidewell, Kenneth D.M. Harris
Journal of Solid State Chemistry 2006 Volume 179(Issue 5) pp:1335-1338
Publication Date(Web):May 2006
DOI:10.1016/j.jssc.2006.01.047
In solid triphenylmethanol, the molecules are arranged in hydrogen-bonded tetramers, and it is already well established that the hydrogen bonding in this material undergoes a dynamic switching process between different hydrogen bonding arrangements. In addition to this motion, we show here, from solid-state 2H NMR studies of the deuterated material (C6D5)3COH, that each phenyl ring in this material undergoes a 180°-jump reorientation about the C6D5–C(OH) bond, with an activation energy of ca. 50 kJ mol−1. The timescale for the phenyl ring dynamics is several orders of magnitude longer than the timescale for the hydrogen bond dynamics in this material, and is uncorrelated with the dynamics of the hydrogen bonding arrangement.In solid triphenylmethanol, the molecules are arranged in hydrogen-bonded tetramers as shown; dynamic properties of this material are investigated here using solid-state 2H NMR spectroscopy.
Co-reporter:Zhigang Pan, Mingcan Xu, Eugene Y. Cheung, James A. Platts, Kenneth D.M. Harris, Edwin C. Constable, Catherine E. Housecroft
Journal of Solid State Chemistry 2006 Volume 179(Issue 10) pp:3214-3223
Publication Date(Web):October 2006
DOI:10.1016/j.jssc.2006.06.009
Structural properties of 2,4,6-trimethoxybenzaldehyde, 2,4,6-trimethoxybenzyl alcohol and 2,4,6-trimethoxyacetophenone have been determined directly from powder X-ray diffraction data, using the direct-space Genetic Algorithm (GA) technique for structure solution followed by Rietveld refinement. Structural similarities and contrasts within this family of materials are elucidated. The work illustrates the value of utilizing information from other sources, including spectroscopic data and computational techniques, as a means of augmenting the structural knowledge established from the powder X-ray diffraction data.
Co-reporter:Zhongfu Zhou Dr.
ChemPhysChem 2006 Volume 7(Issue 8) pp:1649-1653
Publication Date(Web):3 AUG 2006
DOI:10.1002/cphc.200600278
Designer materials: The authors propose a design strategy for a quasicrystalline material composed of discrete molecular entities. The molecular quasicrystal (see figure), which is based on a standard Penrose tiling, is energetically stable and gives rise to a 10-fold symmetric diffraction pattern. The strategy may be further exploited to design molecular quasicrystals based on a range of different types of quasiperiodic arrays.
Co-reporter:Sang-Ok Lee, Benson M. Kariuki and Kenneth D. M. Harris
New Journal of Chemistry 2005 vol. 29(Issue 10) pp:1266-1271
Publication Date(Web):09 Aug 2005
DOI:10.1039/B502004M
Structural features of the urea inclusion compounds containing 1 ∶ 1 mixtures of α,ω-diaminoalkane and α,ω-dihydroxyalkane guest molecules, reported in this paper, provide interesting contrasts to those of conventional urea inclusion compounds. All the α,ω-diaminoalkane/α,ω-dihydroxyalkane/urea inclusion compounds reported have a hydrogen-bonded chain of alternating α,ω-diaminoalkane and α,ω-dihydroxyalkane guest molecules, which is surrounded by urea molecules in a manner that bears some resemblance to the conventional urea tunnel structure, but with the urea–urea hydrogen bonding scheme disrupted by the formation of N–H⋯O hydrogen bonds between NH2 groups of the urea molecules and OH groups of the α,ω-dihydroxyalkane molecules. As a consequence, the guest and host components have the same periodicity, and these inclusion compounds are commensurate, in contrast to conventional urea inclusion compounds. So far, attempts to prepare α,ω-diaminoalkane/α,ω-dihydroxyalkane/urea inclusion compounds for α,ω-dihydroxyalkanes longer than 1,3-dihydroxypropane have been unsuccessful, suggesting that there may be an upper limit to the length of the α,ω-dihydroxyalkane component in this family of structures.
Co-reporter:Shinbyoung Ahn Dr.;J. PrakashaReddy;Benson M. Kariuki Dr.;Swati Chatterjee Dr.;Anupama Ranganathan Dr.;V. R. Pedireddi Dr.;C. N. R. Rao
Chemistry - A European Journal 2005 Volume 11(Issue 8) pp:
Publication Date(Web):4 FEB 2005
DOI:10.1002/chem.200400340
Crystallisation of trithiocyanuric acid (TTCA) from various organic solvents that have hydrogen bonding capability (acetone, 2-butanone, dimethylformamide, dimethyl sulfoxide, methanol and acetonitrile) leads to the formation of co-crystals in which the solvent molecules are incorporated together with TTCA in the crystal structure. Structure determination by single-crystal X-ray diffraction reveals that these co-crystals can be classified into different groups depending upon the topological arrangement of the TTCA molecules in the crystal structure. Thus, three different types of single-tape arrangements of TTCA molecules and one type of double-tape arrangement of TTCA molecules are identified. In all co-crystals, hydrogen-bonding interactions are formed through the involvement of NH bonds of TTCA molecules in these tapes and the other molecule in the co-crystal. Detailed rationalisation of the structural properties of these co-crystals is presented.
Co-reporter:Kenneth D. M. Harris and Eugene Y. Cheung
Chemical Society Reviews 2004 vol. 33(Issue 8) pp:526-538
Publication Date(Web):22 Sep 2004
DOI:10.1039/B409059B
Many crystalline solids cannot be prepared as single crystals of sufficient size and/or quality for structure determination to be carried out using single crystal X-ray diffraction techniques. In such cases, when only polycrystalline powders of a material are available, it is necessary instead to tackle structure determination using powder X-ray diffraction. This article highlights recent developments in the opportunities for determining crystal structures directly from powder diffraction data, focusing on the case of molecular solids and giving particular attention to the most challenging stage of the structure determination process, namely the structure solution stage. In particular, the direct-space strategy for structure solution is highlighted, as this approach has opened up new opportunities for the structure determination of molecular solids. The article gives an overview of the current state-of-the-art in structure determination of molecular solids from powder diffraction data. Relevant fundamental aspects of the techniques in this field are described, and examples are given to highlight the application of these techniques to determine crystal structures of molecular materials.
Co-reporter:Lily Yeo, Kenneth D.M. Harris
Mendeleev Communications 2004 Volume 14(Issue 6) pp:263-266
Publication Date(Web):2004
DOI:10.1070/MC2004v014n06ABEH002028
Computational studies of the extent and nature of host–guest chiral discrimination in incommensurate 2-hydroxyalkane/urea inclusion compounds demonstrate a number of contrasting features between the 2-hydroxyalkane/urea inclusion compounds reported here and 2-bromoalkane/urea inclusion compounds reported previously.
Co-reporter:Colan E. Hughes, Kenneth D.M. Harris
Solid State Nuclear Magnetic Resonance (November 2016) Volume 80() pp:7-13
Publication Date(Web):November 2016
DOI:10.1016/j.ssnmr.2016.10.002
Co-reporter:Kotaro Fujii, Mark T. Young, Kenneth D.M. Harris
Journal of Structural Biology (June 2011) Volume 174(Issue 3) pp:461-467
Publication Date(Web):1 June 2011
DOI:10.1016/j.jsb.2011.03.001
We report the crystal structure of the 5-residue peptide acetyl-YEQGL-amide, determined directly from powder X-ray diffraction data recorded on a conventional laboratory X-ray powder diffractometer. The YEQGL motif has a known biological role, as a trafficking motif in the C-terminus of mammalian P2X4 receptors. Comparison of the crystal structure of acetyl-YEQGL-amide determined here and that of a complex formed with the μ2 subunit of the clathrin adaptor protein complex AP2 reported previously, reveals differences in conformational properties, although there are nevertheless similarities concerning aspects of the hydrogen-bonding arrangement and the hydrophobic environment of the leucine sidechain. Our results demonstrate the potential for exploiting modern powder X-ray diffraction methodology to achieve complete structure determination of materials of biological interest that do not crystallize as single crystals of suitable size and quality for single-crystal X-ray diffraction.
Co-reporter:Zhongfu Zhou and Kenneth D. M. Harris
Physical Chemistry Chemical Physics 2008 - vol. 10(Issue 48) pp:NaN7269-7269
Publication Date(Web):2008/10/31
DOI:10.1039/B807326K
A new strategy for implementing the concept of a “micro genetic algorithm” within a standard genetic algorithm (GA) procedure is proposed. The strategy operates by applying criteria to test for the occurrence of stagnation within the population of a standard GA calculation, and triggering the micro-GA procedure whenever stagnation is detected. The micro-GA is implemented in terms of the parallel evolution of a number of small sub-populations (comprising predominantly new randomly generated structures together with a few of the best structures from the stagnated population), and the sub-population of highest quality following the micro-GA procedure is used in the construction of the next population of the standard GA calculation. The micro-GA procedure is applied in the context of a GA for carrying out direct-space structure solution from powder X-ray diffraction data, and the results demonstrate that this strategy is an effective means of promoting structural diversity within a stagnated population, leading to significantly improved evolutionary progress. This strategy may prove to be more generally applicable as an approach for alleviating problems due to stagnation in GA calculations in other fields of application.
Co-reporter:Colan E. Hughes, G. N. Manjunatha Reddy, Stefano Masiero, Steven P. Brown, P. Andrew Williams and Kenneth D. M. Harris
Chemical Science (2010-Present) 2017 - vol. 8(Issue 5) pp:
Publication Date(Web):
DOI:10.1039/C7SC00587C
Co-reporter:Benjamin A. Palmer, Benson M. Kariuki, Vamsee K. Muppidi, Colan E. Hughes and Kenneth D. M. Harris
Chemical Communications 2011 - vol. 47(Issue 13) pp:NaN3762-3762
Publication Date(Web):2011/02/03
DOI:10.1039/C0CC05477A
X-Ray diffraction studies reveal that the tunnel inclusion compound formed between 1-tert-butyl-4-iodobenzene and thiourea has an incommensurate relationship between the periodicities of the host and guest substructures along the tunnel axis, representing the first reported case of an incommensurate thiourea inclusion compound.
Co-reporter:Kotaro Fujii, Ana Lazuen Garay, Janeen Hill, Elena Sbircea, Zhigang Pan, Mingcan Xu, David C. Apperley, Stuart L. James and Kenneth D. M. Harris
Chemical Communications 2010 - vol. 46(Issue 40) pp:NaN7574-7574
Publication Date(Web):2010/09/17
DOI:10.1039/C0CC02635B
Powder X-ray diffraction (XRD) has been exploited to establish the structural properties of a porous interpenetrated mixed-ligand metal–organic framework material prepared by solid-state grinding, recognizing that product phases from mechanochemical synthesis are typically microcrystalline powders. The importance of subjecting the powder XRD data to rigorous scrutiny in such applications is emphasized.
Co-reporter:Colan E. Hughes and Kenneth D. M. Harris
Chemical Communications 2010 - vol. 46(Issue 27) pp:NaN4984-4984
Publication Date(Web):2010/05/27
DOI:10.1039/C0CC01007C
Application of a technique developed for in situ solid-state 13C NMR studies of crystallization processes reveals direct evidence that crystallization of glycine from a methanol/water solution involves the initial transient formation of the β polymorph, which then undergoes a solution-mediated polymorphic transformation to yield the more stable α polymorph.
Co-reporter:James A. Platts, Hasmerya Maarof, Kenneth D. M. Harris, Gin Keat Lim and David J. Willock
Physical Chemistry Chemical Physics 2012 - vol. 14(Issue 34) pp:NaN11952-11952
Publication Date(Web):2012/07/12
DOI:10.1039/C2CP41716B
Ab initio and density functional theory (DFT) calculations on some model systems are presented to assess the extent to which intermolecular hydrogen bonding can affect the planarity of amide groups. Formamide and urea are examined as archetypes of planar and non-planar amides, respectively. DFT optimisations suggest that appropriately disposed hydrogen-bond donor or acceptor molecules can induce non-planarity in formamide, with OCNH dihedral angles deviating by up to ca. 20° from planarity. Ab initio energy calculations demonstrate that the energy required to deform an amide molecule from the preferred geometry of the isolated molecule is more than compensated by the stabilisation due to hydrogen bonding. Similarly, the NH2 group in urea can be made effectively planar by the presence of appropriately positioned hydrogen-bond acceptors, whereas hydrogen-bond donors increase the non-planarity of the NH2 group. Small clusters (a dimer, two trimers and a pentamer) extracted from the crystal structure of urea indicate that the crystal field acts to force planarity of the urea molecule; however, the interaction with nearest neighbours alone is insufficient to induce the molecule to become completely planar, and longer-range effects are required. Finally, the potential for intermolecular hydrogen bonding to induce non-planarity in a model of a peptide is explored. Inter alia, the insights obtained in the present work on the extent to which the geometry of amide groups may be deformed under the influence of intermolecular hydrogen bonding provide structural guidelines that can assist the interpretation of the geometries of such groups in structure determination from powder X-ray diffraction data.
Co-reporter:Massimo Mella and Kenneth D. M. Harris
Physical Chemistry Chemical Physics 2009 - vol. 11(Issue 47) pp:NaN11346-11346
Publication Date(Web):2009/10/27
DOI:10.1039/B911556K
Computational techniques (second order Møller–Plesset MP2 perturbation theory in conjunction with medium and large size basis sets) are applied to explore structural aspects of a hydrogen-bonded tetrameric cluster of methanol molecules, based geometrically on a tetrahedral arrangement of the four oxygen atoms of the cluster. The hydrogen-bonded structures that represent minima on the potential energy surface are established, and the complete set of pathways that allow interconversion between these structures through “switching” of the hydrogen bonding arrangement are elucidated. The implications of these results in terms of dynamic properties of the cluster are discussed.
Co-reporter:Emilie Courvoisier, P. Andrew Williams, Gin Keat Lim, Colan E. Hughes and Kenneth D. M. Harris
Chemical Communications 2012 - vol. 48(Issue 22) pp:NaN2763-2763
Publication Date(Web):2012/01/12
DOI:10.1039/C2CC17203H
We report the crystal structure of L-arginine, one of the last remaining natural amino acids for which the crystal structure has never been determined; structure determination was carried out directly from powder X-ray diffraction (XRD) data, exploiting the direct-space genetic algorithm technique for structure solution followed by Rietveld refinement.
Co-reporter:Kotaro Fujii, Yasunari Ashida, Hidehiro Uekusa, Fang Guo and Kenneth D. M. Harris
Chemical Communications 2010 - vol. 46(Issue 24) pp:NaN4266-4266
Publication Date(Web):2010/05/12
DOI:10.1039/C0CC00233J
The methanol solvate crystalline phase (M) of benzene-1,2,4,5-tetracarboxylic acid transforms selectively to a hydrate phase (H) or a non-solvate phase (N) depending on the presence of atmospheric water vapour; knowledge of the crystal structures of M and N, determined here using single-crystal and powder X-ray diffraction, respectively, yields insights into mechanistic aspects of the solid-state transformations.
