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43 items found (0 items not approved), displaying 1 to 10.[First/Prev] 1, 2, 3, 4, 5 [Next/Last]

Instruments / Technical Area	Publication Details	Published
I19-Small Molecule Single Crystal Diffraction	Guest-mediated phase transitions in a flexible pillared-layered metal-organic framework under high-pressure Gemma F. Turner , Scott C. Mckellar , David Robert Allan , Anthony K. Cheetham , Sebastian Henke , Stephen A. Moggach Chemical Science DOI: 10.1039/D1SC03108B Open Access Show Abstract ▼ Abstract: The guest-dependent flexibility of the pillared-layered metal-organic framework (MOF), Zn2bdc2dabco·X(guest), where guest = EtOH, DMF or benzene, has been examined by high-pressure single crystal X-ray diffraction. A pressure-induced structural phase transition is found for the EtOH- and DMF-included frameworks during compression in a hydrostatic medium of the guest species, which is dependent upon the nature and quantity of the guest in the channels. The EtOH-included material undergoes a phase transition from P4/mmm to C2/m at 0.69 GPa, which is accompanied by a change in the pore shape from square to rhombus via super-filling of the pores. The DMF-included material undergoes a guest-medaited phase transition from I4/mcm to P4/mmm at 0.32 GPa via disordering of the DMF guest. In contrast, the benzene-included framework features a structure with rhombus-shaped channels at ambient pressure and shows direct compression as well as negative linear compressibility parallel to the long diagonal of the channels under hydrostatic pressure. These results demonstrate the large influence of guest molecules on the phase behavior of flexible MOFs. Thus, guest-mediated framework flexibility is useful to engineering MOFs with bespoke pore shapes and compressibility.	Sep 2021
I19-Small Molecule Single Crystal Diffraction	Evaluating the high-pressure structural response and crystal lattice interactions of the magnetically-bistable organic radical TTTA Jonathan G. Richardson , Asato Mizuno , Yoshiaki Shuku , Kunio Awaga , Neil Robertson , Carole A. Morrison , Mark R. Warren , David R. Allan , Stephen A. Moggach Crystengcomm 2 DOI: 10.1039/D1CE00577D Diamond Proposal Number(s): [19178] Show Abstract ▼ Abstract: Magnetic bistability has previously been observed and evaluated in an organic thiazyl radical 1,3,5-triathia-2,4,6-triazapentalenyl (TTTA). Herein, the structure-pressure response of TTTA has been evaluated by X-ray diffraction, where a lack of a structural phase transition up to 4.6 GPa certifies that the paramagnetic suppression is caused by a steady decrease in the separation between the moieties containing the radical electron along the π-stacking chains. The intermolecular interactions throughout the crystal lattice have also been calculated using the PIXEL method, and highlight the relative strength of the inter-column interactions in the two known polymorphs of TTTA, which provides extra justification for the cause of the wide magnetic hysteresis and its response to pressure.	May 2021
I19-Small Molecule Single Crystal Diffraction	High-pressure sapphire capillary cell for synchrotron single-crystal X-ray diffraction measurements to 1500 bar Charles J. Mcmonagle , David R. Allan , Mark R. Warren , Konstantin V. Kamenev , Gemma F. Turner , Stephen A. Moggach Journal Of Applied Crystallography 53 DOI: 10.1107/S1600576720013710 Diamond Proposal Number(s): [15190, 14164] Show Abstract ▼ Abstract: A new sapphire capillary pressure cell for single-crystal X-ray diffraction measurements at moderate pressures (200−1500 bar; 1 bar = 100 kPa) has been developed and optimized for use on beamline I19 at Diamond Light Source. The three-component cell permits optical centring of the crystal and in situ pressure modification to a precision of 1 bar. Compression of hexamethylenetetramine and its deuterated analogue to 1000 bar was performed, showcasing the accuracy and precision of the measurements, and highlighting evidence of a geometric isotope effect.	Dec 2020
	Pressure-and temperature induced phase transitions, piezochromism, NLC behaviour and pressure controlled Jahn–Teller switching in a Cu-based framework Charles J. Mcmonagle , Priyanka Comar , Gary S. Nichol , David R. Allan , Jesús González , José A. Barreda-Argüeso , Fernando Rodríguez , Rafael Valiente , Gemma F. Turner , Euan K. Brechin , Stephen A. Moggach Chemical Science 11, 8793 - 8799 DOI: 10.1039/D0SC03229H Open Access Show Abstract ▼ Abstract: In situ single-crystal diffraction and spectroscopic techniques have been used to study a previously unreported Cu-framework bis[1-(4-pyridyl)butane-1,3-dione]copper(II) (CuPyr-I). CuPyr-I was found to exhibit high-pressure and low-temperature phase transitions, piezochromism, negative linear compressibility, and a pressure induced Jahn–Teller switch, where the switching pressure was hydrostatic media dependent.	Aug 2020
I19-Small Molecule Single Crystal Diffraction	Probing the structural and electronic response of Magnus green salt compounds [Pt(NH2R)4][PtCl4] (R=H, CH3) to pressure Jonathan G. Richardson , Helen Benjamin , Stephen A. Moggach , Lisette R Warren , Mark R. Warren , David R. Allan , Lucy K. Saunders , Carole A. Morrison , Neil Robertson Physical Chemistry Chemical Physics DOI: 10.1039/D0CP03280H Diamond Proposal Number(s): [19178] Open Access Show Abstract ▼ Abstract: Despite possessing the desirable crystal packing and short Pt···Pt stacking distances required for a large piezoresistive response, the conductivity-pressure response of the Magnus green salt [Pt(NH3)4][PtCl4] is extremely sluggish. Through a combination of high-pressure X-ray diffraction and hybrid-DFT solid state calculations this study demonstrates that the poor conductivity-pressure response is due to a low volumetric compression anisotropy, a relatively large ambient pressure band gap and a lack of dispersion in the conduction band. Ligand modification (from NH3 to NH2CH3) does not enhance the piezoresistive response, causing even lower anisotropy of the volumetric compression and an unexpected phase transition at above 2 GPa. This study demonstrates that consideration of frontier band dispersion is a key design criterion, alongside crystal packing and Pt···Pt stacking distances for piezoresistive materials.	Jul 2020
I19-Small Molecule Single Crystal Diffraction	Pressure-induced non-innocence in bis(1,2-dionedioximato)Pt( ii ) complexes: an experimental and theoretical study of their insulator–metal transitions Helen Benjamin , Jonathan G. Richardson , Stephen A. Moggach , Sergejs Afanasjevs , Lisette Warren , Mark Warren , David R. Allan , Carole A. Morrison , Konstantin V. Kamenev , Neil Robertson Physical Chemistry Chemical Physics 134 DOI: 10.1039/C9CP06749C Diamond Proposal Number(s): [19178] Open Access Show Abstract ▼ Abstract: Bis(1,2-dionedioximato) complexes of Pt(II) are known for their propensity to form linear chains of metal complexes in the solid state, and under the application of pressure members of the family display interesting optical and conductive properties. Two examples, Pt(bqd)2 and Pt(dmg)2, are known to undergo insulator-to-metal-to-insulator transitions, with the metallic state reached at 0.8–1.4 GPa and 5 GPa, respectively. Previous interpretations of these materials’ behaviour focused on the role of the filled dz2 and vacant p orbitals on platinum, with little consideration to the role of the ligand. Here, the pressure-structural behaviour of Pt(bqd)2 is investigated through single crystal X-ray diffraction, the first such study on this material. The difference in conductive behaviour under pressure between Pt(bqd)2 and Pt(dmg)2 is then interpreted through a combination of experimental and computational methods, including conductivity measurements under high pressure and electronic structure calculations. Our computational work reveals the significant contribution from ligand low-lying vacant π-orbitals to the frontier orbitals and bands in these complexes, and provides an explanation for the experimentally observed re-entrant insulator-to-metal-to-insulator transitions, and the differences in behaviour between the two compounds.	Mar 2020
I19-Small Molecule Single Crystal Diffraction	Highly stable fullerene-based porous molecular crystals with open metal sites C. Grazia Bezzu , Luke A. Burt , Charles J. Mcmonagle , Stephen A. Moggach , Benson M. Kariuki , David R. Allan , Mark Warren , Neil B. Mckeown Nature Materials 348 DOI: 10.1038/s41563-019-0361-0 Diamond Proposal Number(s): [9816, 8945] Show Abstract ▼ Abstract: The synthesis of conventional porous crystals involves building a framework using reversible chemical bond formation, which can result in hydrolytic instability. In contrast, porous molecular crystals assemble using only weak intermolecular interactions, which generally do not provide the same environmental stability. Here, we report that the simple co-crystallization of a phthalocyanine derivative and a fullerene (C60 or C70) forms porous molecular crystals with environmental stability towards high temperature and hot aqueous base or acid. Moreover, by using diamond anvil cells and synchrotron single-crystal measurements, stability towards extreme pressure (>4 GPa) is demonstrated, with the stabilizing fullerene held between two phthalocyanines and the hold tightening at high pressure. Access to open metal centres within the porous molecular co-crystal is demonstrated by in situ crystallographic analysis of the chemisorption of pyridine, oxygen and carbon monoxide. This suggests strategies for the formation of highly stable and potentially functional porous materials using only weak van der Waals intermolecular interactions.	May 2019
I19-Small Molecule Single Crystal Diffraction	Tuning the Swing Effect by Chemical Functionalisation of Zeolitic Imidazolate Frameworks Claire L. Hobday , Thomas D. Bennett , David Fairen-jimenez , Alexander J. Graham , Carole A. Morrison , David R. Allan , Tina Düren , Stephen A. Moggach Journal Of The American Chemical Society DOI: 10.1021/jacs.7b10897 Show Abstract ▼ Abstract: Many zeolitic imidazolate frameworks (ZIFs) are promising candidates for use in separation technologies. Comprising large cavities interconnected by small windows they can be used, at least in principle, as molecular sieves where molecules smaller than the window size are able to diffuse into the material while larger are rejected. However, “swing effect” or “gate opening” phenomena resulting in an enlargement of the windows have proven to be detrimental. Here, we present the first systematic experimental and computational study of the effect of chemical functionalisation of the imidazole linker on the framework dynamics. Using high-pressure (HP) single-crystal X-ray diffraction, density functional theory, and grand canonical Monte Carlo simulations, we show that in the isostructural ZIF-8, ZIF-90 and ZIF-65 functional groups of increasing polarity (-CH3,-CHO, -NO2) on the imidazole linkers provide control over the degree of rotation and thus the critical window diameter. On application of pressure, the substituted imidazolate rings rotate resulting in an increase in both pore volume and content. Our results show that the interplay between the guest molecules and the chemical function of the imidazole linker is essential for directing the swing effect in ZIF frameworks and therefore the adsorption performance.	Dec 2017
I19-Small Molecule Single Crystal Diffraction	Hidden negative linear compressibility in lithium l-tartrate Hamish H.-m. Yeung , Rebecca Kilmurray , Claire Hobday , Scott C. Mckellar , Anthony K. Cheetham , David R. Allan , Stephen A. Moggach Phys. Chem. Chem. Phys. DOI: 10.1039/C6CP08690J Diamond Proposal Number(s): [9700] Show Abstract ▼ Abstract: By decoupling the mechanical behaviour of building units for the first time in a wine-rack framework containing two different strut types, we show that lithium l-tartrate exhibits NLC with a maximum value, Kmax = -21 TPa-1, and an overall NLC capacity, ΧNLC = 5.1 %, that are comparable to the most exceptional materials to date. Furthermore, the contributions from molecular strut compression and angle opening interplay to give rise to so-called “hidden” negative linear compressibility, in which NLC is absent at ambient pressure, switched on at 2 GPa and sustained up to the limit of our experiment, 5.5 GPa. Analysis of the changes in crystal structure using variable-pressure synchrotron X-ray diffraction reveals new chemical and geometrical design rules to assist the discovery of other materials with exciting hidden anomalous mechanical properties.	Jan 2017
I19-Small Molecule Single Crystal Diffraction	Pressure induced enhancement of the magnetic ordering temperature in rhenium(IV) monomers Christopher H. Woodall , Gavin A. Craig , Alessandro Prescimone , Martin Misek , Joan Cano , Juan Faus , Michael R. Probert , Simon Parsons , Stephen Moggach , José Martínez-lillo , Mark Murrie , Konstantin V. Kamenev , Euan K. Brechin Nature Communications 7 DOI: 10.1038/ncomms13870 Diamond Proposal Number(s): [11879] Open Access Show Abstract ▼ Abstract: Materials that demonstrate long-range magnetic order are synonymous with information storage and the electronics industry, with the phenomenon commonly associated with metals, metal alloys or metal oxides and sulfides. A lesser known family of magnetically ordered complexes are the monometallic compounds of highly anisotropic d-block transition metals; the ‘transformation’ from isolated zero-dimensional molecule to ordered, spin-canted, three-dimensional lattice being the result of through-space interactions arising from the combination of large magnetic anisotropy and spin-delocalization from metal to ligand which induces important intermolecular contacts. Here we report the effect of pressure on two such mononuclear rhenium(IV) compounds that exhibit long-range magnetic order under ambient conditions via a spin canting mechanism, with Tc controlled by the strength of the intermolecular interactions. As these are determined by intermolecular distance, ‘squeezing’ the molecules closer together generates remarkable enhancements in ordering temperatures, with a linear dependence of Tc with pressure.	Dec 2016

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