I11-High Resolution Powder Diffraction
I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[15777, 17193]
Open Access
Abstract: Organic molecules tend to close pack to form dense structures when they are crystallised from organic solvents. Porous molecular crystals defy this rule: they contain open space, which is typically stabilised by inclusion of solvent in the interconnected pores during crystallisation. The design and discovery of such structures is often challenging and time consuming, in part because it is difficult to predict solvent effects on crystal form stability. Here, we combine crystal structure prediction (CSP) with a robotic crystallisation screen to accelerate the discovery of stable hydrogen-bonded frameworks. We exemplify this strategy by finding new phases of two well-studied molecules in a computationally targeted way. Specifically, we find a new ‘hidden’ porous polymorph of trimesic acid, δ-TMA, that has a guest-free hexagonal pore structure, as well as three new solvent-stabilized diamondoid frameworks of adamantane-1,3,5,7-tetracarboxylic acid (ADTA). Beyond porous solids, this hybrid computational–experimental approach could be applied to a wide range of materials problems, such as organic electronics and drug formulation.
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Sep 2019
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I11-High Resolution Powder Diffraction
I19-Small Molecule Single Crystal Diffraction
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Kecheng
Jie
,
Ming
Liu
,
Yujuan
Zhou
,
Marc A.
Little
,
Angeles
Pulido
,
Samantha Y.
Chong
,
Andrew
Stephenson
,
Ashlea R.
Hughes
,
Fumiyasu
Sakakibara
,
Tomoki
Ogoshi
,
Frédéric
Blanc
,
Graeme M.
Day
,
Feihe
Huang
,
Andrew I.
Cooper
Diamond Proposal Number(s):
[15777, 12336, 17193]
Abstract: The energy-efficient separation of alkylaromatic compounds is a major industrial sustainability challenge. The use of selectively porous extended frameworks, such as zeolites or metal–organic frameworks, is one solution to this problem. Here, we studied a flexible molecular material, perethylated pillar[n]arene crystals (n = 5, 6), which can be used to separate C8 alkylaromatic compounds. Pillar[6]arene is shown to separate para-xylene from its structural isomers, meta-xylene and ortho-xylene, with 90% specificity in the solid state. Selectivity is an intrinsic property of the pillar[6]arene host, with the flexible pillar[6]arene cavities adapting during adsorption thus enabling preferential adsorption of para-xylene in the solid state. The flexibility of pillar[6]arene as a solid sorbent is rationalized using molecular conformer searches and crystal structure prediction (CSP) combined with comprehensive characterization by X-ray diffraction and 13C solid state NMR spectroscopy. The CSP study, which takes into account the structural variability of pillar[6]arene, breaks new ground in its own right and showcases the feasibility of applying CSP methods to understand and ultimately to predict the behaviour of soft, adaptive molecular crystals.
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May 2018
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I11-High Resolution Powder Diffraction
I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[15777, 12336]
Open Access
Abstract: Crystal structure prediction methods can enable the in silico design of functional molecular crystals, but solvent effects can have a major influence on relative lattice energies, sometimes thwarting predictions. This is particularly true for porous solids, where solvent included in the pores can have an important energetic contribution. We present a Monte Carlo solvent insertion procedure for predicting the solvent filling of porous structures from crystal structure prediction landscapes, tested using a highly solvatomorphic porous organic cage molecule, CC1. Using this method, we can understand why the predicted global energy minimum structure for CC1 is never observed from solvent crystallisation. We also explain the formation of three different solvatomorphs of CC1 from three structurally-similar chlorinated solvents. Calculated solvent stabilisation energies are found to correlate with experimental results from thermogravimetric analysis, suggesting a future computational framework for a priori materials design that factors in solvation effects.
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Apr 2018
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I19-Small Molecule Single Crystal Diffraction
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Anna G.
Slater
,
Paul S.
Reiss
,
Angeles
Pulido
,
Marc A.
Little
,
Daniel L.
Holden
,
Linjiang
Chen
,
Samantha Y.
Chong
,
Ben M.
Alston
,
Rob
Clowes
,
Maciej
Haranczyk
,
Michael E.
Briggs
,
Tom
Hasell
,
Graeme M.
Day
,
Andrew I.
Cooper
Diamond Proposal Number(s):
[11231, 12336]
Open Access
Abstract: The physical properties of 3-D porous solids are defined by their molecular geometry. Hence, precise control of pore size, pore shape, and pore connectivity are needed to tailor them for specific applications. However, for porous molecular crystals, the modification of pore size by adding pore-blocking groups can also affect crystal packing in an unpredictable way. This precludes strategies adopted for isoreticular metal–organic frameworks, where addition of a small group, such as a methyl group, does not affect the basic framework topology. Here, we narrow the pore size of a cage molecule, CC3, in a systematic way by introducing methyl groups into the cage windows. Computational crystal structure prediction was used to anticipate the packing preferences of two homochiral methylated cages, CC14-R and CC15-R, and to assess the structure–energy landscape of a CC15-R/CC3-S cocrystal, designed such that both component cages could be directed to pack with a 3-D, interconnected pore structure. The experimental gas sorption properties of these three cage systems agree well with physical properties predicted by computational energy–structure–function maps.
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Jun 2017
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I11-High Resolution Powder Diffraction
I19-Small Molecule Single Crystal Diffraction
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Angeles
Pulido
,
Linjiang
Chen
,
Tomasz
Kaczorowski
,
Daniel
Holden
,
Marc A.
Little
,
Samantha Y.
Chong
,
Benjamin J.
Slater
,
David P.
Mcmahon
,
Baltasar
Bonillo
,
Chloe J.
Stackhouse
,
Andrew
Stephenson
,
Christopher M.
Kane
,
Rob
Clowes
,
Tom
Hasell
,
Andrew I.
Cooper
,
Graeme M.
Day
Diamond Proposal Number(s):
[8728, 12336]
Abstract: Molecular crystals cannot be designed in the same manner as macroscopic objects, because they do not assemble according to simple, intuitive rules. Their structures result from the balance of many weak interactions, rather than from the strong and predictable bonding patterns found in metal–organic frameworks and covalent organic frameworks. Hence, design strategies that assume a topology or other structural blueprint will often fail. Here we combine computational crystal structure prediction and property prediction to build energy–structure–function maps that describe the possible structures and properties that are available to a candidate molecule. Using these maps, we identify a highly porous solid, which has the lowest density reported for a molecular crystal so far. Both the structure of the crystal and its physical properties, such as methane storage capacity and guest-molecule selectivity, are predicted using the molecular structure as the only input. More generally, energy–structure–function maps could be used to guide the experimental discovery of materials with any target function that can be calculated from predicted crystal structures, such as electronic structure or mechanical properties.
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Mar 2017
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I11-High Resolution Powder Diffraction
I19-Small Molecule Single Crystal Diffraction
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Tom
Hasell
,
Jamie L.
Culshaw
,
Sam
Chong
,
Marc
Schmidtmann
,
Marc
Little
,
Kim E
Jelfs
,
Edward O
Pyzer-knapp
,
Hilary
Shepherd
,
Dave
Adams
,
Graeme M.
Day
,
Andrew I.
Cooper
Diamond Proposal Number(s):
[7040, 8728]
Abstract: Small structural changes in organic molecules can have a large influence on solid-state crystal packing, and this often thwarts attempts to produce isostructural series of crystalline solids. For metal–organic frameworks and covalent organic frameworks, this has been addressed by using strong, directional intermolecular bonding to create families of isoreticular solids. Here, we show that an organic directing solvent, 1,4-dioxane, has a dominant effect on the lattice energy for a series of organic cage molecules. Inclusion of dioxane directs the crystal packing for these cages away from their lowest-energy polymorphs to form isostructural, 3-dimensional diamondoid pore channels. This is a unique function of the size, chemical function, and geometry of 1,4-dioxane, and hence, a noncovalent auxiliary interaction assumes the role of directional coordination bonding or covalent bonding in extended crystalline frameworks. For a new cage, CC13, a dual, interpenetrating pore structure is formed that doubles the gas uptake and the surface area in the resulting dioxane-directed crystals.
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Jan 2014
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I11-High Resolution Powder Diffraction
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Abstract: The search for materials capable of storing small molecular species is experiencing a shift from solids with permanent porosity towards organic materials capable of the uptake and release of low- molecular-weight guests. We demonstrate that a solid mixture of the pharmaceutical compound lamotrigine with a range of saturated and unsaturated 1,4-butanedicarboxylic acids, when in combination with a third molecule, can result in the formation of a family of isostructural materials involving a structurally persistent binary-host framework based on a hydrogen-bonded molecular salt of lamotrigine and the acid. A systematic study, based on mechanochemical screening, has revealed a remarkable robustness to subtle changes in the chemical functionality of the acid in that at least 12 different acids can be used in combination with lamotrigine to generate isostructural binary-host frameworks. Such robust isostructurality results in the important attribute that the shape, size and surface chemistry of the inclusion cavities can be fine-tuned by systematic variation of the substituents on the dicarboxylic acid.
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Jul 2012
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I19-Small Molecule Single Crystal Diffraction
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James T. A.
Jones
,
Tom
Hasell
,
Xiaofeng
Wu
,
John
Bacsa
,
Kim E.
Jelfs
,
Marc
Schmidtmann
,
Samantha Y.
Chong
,
Dave J.
Adams
,
Abbie
Trewin
,
Florian
Schiffman
,
Furio
Cora
,
Ben
Slater
,
Alexander
Steiner
,
Graeme M.
Day
,
Andrew I.
Cooper
Diamond Proposal Number(s):
[7036]
Abstract: Nanoporous molecular frameworks are important in applications such as separation, storage and catalysis. Empirical rules exist for their assembly but it is still challenging to place and segregate functionality in three-dimensional porous solids in a predictable way. Indeed, recent studies of mixed crystalline frameworks suggest a preference for the statistical distribution of functionalities throughout the pores rather than, for example, the functional group localization found in the reactive sites of enzymes. This is a potential limitations for 'one-pot' chemical syntheses of porous frameworks from simple starting materials. An alternative strategy is to prepare porous solids from synthetically preorganized molecular pores. In principle, functional organic pore modules could be covalently prefabricated and then assembled to produce materials with specific properties. However, this vision of mix-and-match assembly is far from being realized, not least because of the challenge in reliably predicting three-dimensional structures for molecular crystals, which lack the strong directional bonding found in networks. Here we show that highly porous crystalline solids can be produced by mixing different organic cage modules that self-assemble by means of chiral recognition. The structures of the resulting materials can be predicted computationally, allowing in silico materials design strategies. The constituent pore modules are synthesized in high yields on gram scales in a one-step reaction. Assembly of the porous co-crystals is as simple as combining the modules in solution and removing the solvent. In some cases, the chiral recognition between modules can be exploited to produce porous organic nanoparticles. We show that the method is valid for four different cage modules and can in principle be generalized in a computationally predictable manner based on a lock-and-key assembly between modules.
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Jun 2011
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