I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[15833]
Open Access
Abstract: The solid state supramolecular interactions of diketopyrrolopyrrole derivatives (DPPs) and their correlation with thin film optical properties are of particular interest because of the applications of these materials in organic electronics. In this study, we report the single crystal X-ray structures of several phenyl DPP derivatives, containing 4-methoxyphenyl, 4-hydroxyphenyl and 4-((tetrahydro-2H-pyran-2-yl)oxy)phenyl aryl units, and show how subtle changes in the substituent chains at side or end positions of the chromophore can lead to very different packing. They are compared to their phenyl counterpart to explore how the nature of both the alkyl chain and the aryl unit influence the optical properties that have been measured in solid and solution states. Importantly, for the three families of N-substituted compounds studied, the structures are changed by the conformation of the molecules and are apparently dominated by crystal packing effects where edge-to-face interactions are favoured rather than π stacking, with only one of the compounds showing a flat form, promoted by intermolecular contacts between the aromatic regions. It is therefore possible that the twist between DPP and phenyl units in crystals of DPPs results from edge-to-face interactions (rather than steric interactions between the N-substituent and the protons attached to the aromatic ring) that might be overcome in more extended structures. Hydrogen bonding dominates the packing to generate chains of DPP units for phenol derivatives. Remote bulky groups do affect the core conformation. The emission of the materials as thin films is dominated by local effects in the packing of the materials that are unique for each case as the structures are distinct from one another. Charge mobility (as calculated from the crystal structures) is not favoured because of twisted conformations and large displacement, but the sometimes high emission and large Stokes shift could make the materials interesting for other purposes, such as light emitters.
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Feb 2021
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I11-High Resolution Powder Diffraction
I19-Small Molecule Single Crystal Diffraction
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Stephen P.
Argent
,
Ivan
Da Silva
,
Alex
Greenaway
,
Mathew
Savage
,
Jack
Humby
,
Andrew J.
Davies
,
Harriott
Nowell
,
William
Lewis
,
Pascal
Manuel
,
Chiu C.
Tang
,
Alexander J.
Blake
,
Michael W.
George
,
Alexander V.
Markevich
,
Elena
Besley
,
Sihai
Yang
,
Neil R.
Champness
,
Martin
Schroeder
Diamond Proposal Number(s):
[861, 11622, 15833, 9443]
Open Access
Abstract: Designing porous materials which can selectively adsorb CO2 or CH4 is an important environmental and industrial goal which requires an understanding of the host–guest interactions involved at the atomic scale. Metal–organic polyhedra (MOPs) showing permanent porosity upon desolvation are rarely observed. We report a family of MOPs (Cu-1a, Cu-1b, Cu-2), which derive their permanent porosity from cavities between packed cages rather than from within the polyhedra. Thus, for Cu-1a, the void fraction outside the cages totals 56% with only 2% within. The relative stabilities of these MOP structures are rationalized by considering their weak nondirectional packing interactions using Hirshfeld surface analyses. The exceptional stability of Cu-1a enables a detailed structural investigation into the adsorption of CO2 and CH4 using in situ X-ray and neutron diffraction, coupled with DFT calculations. The primary binding sites for adsorbed CO2 and CH4 in Cu-1a are found to be the open metal sites and pockets defined by the faces of phenyl rings. More importantly, the structural analysis of a hydrated sample of Cu-1a reveals a strong hydrogen bond between the adsorbed CO2 molecule and the Cu(II)-bound water molecule, shedding light on previous empirical and theoretical observations that partial hydration of metal−organic framework (MOF) materials containing open metal sites increases their uptake of CO2. The results of the crystallographic study on MOP–gas binding have been rationalized using DFT calculations, yielding individual binding energies for the various pore environments of Cu-1a.
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Oct 2020
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[6410]
Abstract: A strategy to create organic molecules with high degrees of radical spin multiplicity is reported in which molecular design is correlated with the behaviour of radical anions in a series of BODIPY dyads. Upon reduction of each BODIPY moiety radical anions are formed which are shown to have different spin multiplicities by electron paramagnetic resonance (EPR) spectroscopy and distinct profiles in their cyclic voltammograms and UV-visible spectra. The relationship between structure and multiplicity is demonstrated showing that the balance between singlet, biradical or triplet states in the dyads depends on relative orientation and connectivity of the BODIPY groups. The strategy is applied to the synthesis of a BODIPY triad which adopts an unusual quartet state upon reduction to its radical trianion.
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Feb 2020
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I19-Small Molecule Single Crystal Diffraction
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Abstract: A series of symmetrically bis‐4‐methoxybenzyl (4MB) N‐substituted 1,4‐diketopyrrolo[3,4‐c]pyrrole (DPP) derivatives have been synthesized. The 4MB unit makes the DPP core soluble, and shows subtle modification of up to 0.2 eV in ground and excited states of the core when compared with related alkyl derivatives. Absorption and emission spectroscopy, as well as electrochemical and computational methods have been employed to prove the importance of the peripheral aryl units on the donor/ acceptor properties of the molecules. The 4MB products are highly fluorescent (quantum yields approaching 100 % in solution), with a unique distribution of frontier states shown by spectroelectrochemistry. The solid‐state fluorescence correlates with the X‐ray crystal structures of the compounds, a Stokes shift of approximately 80 nm is seen for two of the compounds. The frontier energy levels show that this subtle substitutional change could be of future use in molecular energy level tailoring in these, and related, materials for organic (opto)electronics.
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Jul 2019
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B22-Multimode InfraRed imaging And Microspectroscopy
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Jack
Humby
,
Oguarabau
Benson
,
Gemma L.
Smith
,
Stephen P.
Argent
,
Ivan
Da Silva
,
Yongqiang
Cheng
,
Svemir
Rudic
,
Pascal
Manuel
,
Mark D.
Frogley
,
Gianfelice
Cinque
,
Lucy K.
Saunders
,
Inigo
Vitorica-Yrezabal
,
George F. S.
Whitehead
,
Timothy L.
Easun
,
William
Lewis
,
Alexander J.
Blake
,
Anibal J.
Ramirez-Cuesta
,
Sihai
Yang
,
Martin
Schroeder
Diamond Proposal Number(s):
[13666]
Open Access
Abstract: In order to develop new porous materials for applications in gas separations such as natural gas upgrading, landfill gas processing and acetylene purification it is vital to gain understanding of host-substrate interactions at a molecular level. Herein we report a series of six isoreticular metal-organic frameworks (MOFs) for selective gas adsorption. These materials do not incorporate open metal sites and thus provide an excellent platform to investigate the effect of the incorporation of ligand functionality via amide and alkyne groups on substrate binding. By reducing the linker length of our previously reported MFM-136, we report much improved CO2/CH4 (50:50) and CO2/N¬2 (15:85) selectivity values of 20.2 and 65.4, respectively (1 bar and 273 K), in the new amide-decorated MOF, MFM-126. The CO2 separation performance of MFM-126 has been confirmed by dynamic breakthrough experiments. In situ inelastic neutron scattering and synchrotron FT-IR microspectroscopy were employed to elucidate dynamic interactions of adsorbed CO2 molecules within MFM-126. Upon changing the functionality to an alkyne group in MFM-127, the CO2 uptake decreases but the C2H2 uptake increases by 68%, leading to excellent C2H2/CO2 and C2H2/CH4 selectivities of 3.7 and 21.2, respectively. Neutron powder diffraction enabled the direct observation of the preferred binding domains in MFM-126 and MFM-127, and, to the best of our knowledge, we report the first example of acetylene binding to an alkyne moiety in a porous material, with over 50% of the acetylene observed within MFM-127 displaying interactions (<4 Å) with the alkyne functionality of the framework.
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Oct 2018
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I20-Scanning-X-ray spectroscopy (XAS/XES)
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Ashley J.
Wooles
,
David P.
Mills
,
Floriana
Tuna
,
Eric J. L.
Mcinnes
,
Gareth T. W.
Law
,
Adam J.
Fuller
,
Felipe
Kremer
,
Mark
Ridgway
,
William
Lewis
,
Laura
Gagliardi
,
Bess
Vlaisavljevich
,
Stephen T.
Liddle
Diamond Proposal Number(s):
[9621, 13559]
Open Access
Abstract: Despite the fact that non-aqueous uranium chemistry is over 60 years old, most polarised-covalent uranium-element multiple bonds involve formal uranium oxidation states IV, V, and VI. The paucity of uranium(III) congeners is because, in common with metal-ligand multiple bonding generally, such linkages involve strongly donating, charge-loaded ligands that bind best to electron-poor metals and inherently promote disproportionation of uranium(III). Here, we report the synthesis of hexauranium-methanediide nanometre-scale rings. Combined experimental and computational studies suggest overall the presence of formal uranium(III) and (IV) ions, though electron delocalisation in this Kramers system cannot be definitively ruled out, and the resulting polarised-covalent U = C bonds are supported by iodide and δ-bonded arene bridges. The arenes provide reservoirs that accommodate charge, thus avoiding inter-electronic repulsion that would destabilise these low oxidation state metal-ligand multiple bonds. Using arenes as electronic buffers could constitute a general synthetic strategy by which to stabilise otherwise inherently unstable metal-ligand linkages.
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May 2018
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[8618]
Abstract: The structural characterization of single crystals of di-4-pyridyl-substituted 3,4,9,10-perylenetetracarboxylic diimide reveals a surprising triple helical arrangement. The intermolecular interactions that lead to such an arrangement are investigated by Hirshfeld surface analysis and indicate that the supramolecular structure arises due to a combination of C–H···O interactions and π–π stacking interactions between adjacent perylene diimide (PDI) species. The interplay of these interactions leads to the formation of a tubular structure enclosed by the triple helix of PDI molecules. In contrast, the analogous phenyl-substituted molecule forms a simple one-dimensional stack of PDI molecules which is also unusual in that the perylene core adopts an essentially planar arrangement despite bay substitution.
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Jan 2018
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I19-Small Molecule Single Crystal Diffraction
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Florian
Moreau
,
Daniil I.
Kolokolov
,
Alexander G.
Stepanov
,
Timothy L.
Easun
,
Anne
Dailly
,
William
Lewis
,
Alexander J.
Blake
,
Harriott
Nowell
,
Matthew J.
Lennox
,
Elena
Besley
,
Sihai
Yang
,
Martin
Schröder
Diamond Proposal Number(s):
[12517]
Abstract: Modulation and precise control of porosity of metal-organic frameworks (MOFs) is of critical importance to their materials function. Here we report modulation of porosity for a series of isoreticular octacarboxylate MOFs, denoted MFM-180 to MFM-185, via a strategy of selective elongation of metal-organic cages. Owing to the high ligand connectivity, these MOFs do not show interpenetration, and are robust structures that have permanent porosity. Interestingly, activated MFM-185a shows a high Brunauer–Emmett–Teller (BET) surface area of 4,734 m2 g−1 for an octacarboxylate MOF. These MOFs show remarkable CH4 and CO2 adsorption properties, notably with simultaneously high gravimetric and volumetric deliverable CH4 capacities of 0.24 g g−1 and 163 vol/vol (298 K, 5–65 bar) recorded for MFM-185a due to selective elongation of tubular cages. The dynamics of molecular rotors in deuterated MFM-180a-d16 and MFM-181a-d16 were investigated by variable-temperature 2H solid-state NMR spectroscopy to reveal the reorientation mechanisms within these materials. Analysis of the flipping modes of the mobile phenyl groups, their rotational rates, and transition temperatures paves the way to controlling and understanding the role of molecular rotors through design of organic linkers within porous MOF materials.
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Mar 2017
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[11622]
Open Access
Abstract: Mono- and di-alkylated 1,4-diketo-3,6-dithiophenylpyrrolo[3-4-c]pyrrole derivatives (TDPPs) have been synthesised and their solid state packing and absorption properties have been correlated. In this library of compounds the bulkier substituents distort the geometry of the chromophores and shift the lowest energy absorption band as a consequence of reduced π–π stacking and inter-chromophore overlap. Longitudinal displacement of the conjugated core is affected by donor–acceptor intermolecular interactions and twisting of the thiophene ring out of the plane of the DPP core, whereas lateral displacement was correlated to distortion of the NLactam–C(R) bond out of the plane of the DPP core. The di-substituted TDPP with hexyl units exhibit high molecular planarity, strong close packing of the conjugated core and significant red shift of the maximum of absorption in the solid, whereas the mono-substituted compounds with hexyl and ethyl acetate units are the least distorted of the series because of strong intermolecular hydrogen bonding that increases the molecular overlap and planarity of the chromophores. Therefore the family of mono-substituted TDPPs and more specifically the ones with ethyl acetate substituents show good potential for modulating the molecular geometry and optimizing the charge transport in materials for organic electronic applications.
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Nov 2016
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B22-Multimode InfraRed imaging And Microspectroscopy
I11-High Resolution Powder Diffraction
I19-Small Molecule Single Crystal Diffraction
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Mathew
Savage
,
Yongqiang
Cheng
,
Timothy L.
Easun
,
Jennifer E.
Eyley
,
Stephen P.
Argent
,
Mark
Warren
,
William
Lewis
,
Claire
Murray
,
Chiu C.
Tang
,
Mark D.
Frogley
,
Gianfelice
Cinque
,
Junliang
Sun
,
Svemir
Rudić
,
Richard T.
Murden
,
Michael J.
Benham
,
Andrew N.
Fitch
,
Alexander J.
Blake
,
Anibal J.
Ramirez-Cuesta
,
Sihai
Yang
,
Martin
Schröder
Diamond Proposal Number(s):
[9444, 5839, 12516]
Open Access
Abstract: Selective adsorption of SO2 is realized in a porous metal–organic framework material, and in-depth structural and spectroscopic investigations using X-rays, infrared, and neutrons define the underlying interactions that cause SO2 to bind more strongly than CO2 and N2.
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Aug 2016
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