90 results found
Rice B, LeBlanc LM, Otero-de-la-Roza A, et al., 2018, A computational exploration of the crystal energy and charge-carrier mobility landscapes of the chiral helicene molecule (vol 10, pg 1865, 2018), NANOSCALE, Vol: 10, Pages: 9410-9410, ISSN: 2040-3364
Pugh CJ, Santolini V, Greenaway RL, et al., 2018, Cage doubling: solvent-mediated re-equilibration of a [3+6] prismatic organic cage to a large [6+12] truncated tetrahedron, Crystal Growth and Design, Vol: 18, Pages: 2759-2764, ISSN: 1528-7483
We show that a [3 + 6] trigonal prismatic imine (a) cage can rearrange stoichiometrically and structurally to form a [6 + 12] cage (b) with a truncated tetrahedral shape. Molecular simulations rationalize why this rearrangement was only observed for the prismatic [3 + 6] cage TCC1 but not for the analogous [3 + 6] cages, TCC2 and TCC3. Solvent was found to be a dominant factor in driving this rearrangement.
Meier C, Turkani L, Sprick R, et al., 2018, Integrated experimental and computational high-throughput screening for polymer photocatalysts, 255th National Meeting and Exposition of the American-Chemical-Society (ACS) - Nexus of Food, Energy, and Water, Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
Slater AG, Little MA, Briggs ME, et al., 2018, A solution-processable dissymmetric porous organic cage, MOLECULAR SYSTEMS DESIGN & ENGINEERING, Vol: 3, Pages: 223-227, ISSN: 2058-9689
Rice B, LeBlanc LM, Otero-de-la-Roza A, et al., 2018, A computational exploration of the crystal energy and charge-carrier mobility landscapes of the chiral helicene molecule, Nanoscale, Vol: 10, Pages: 1865-1876, ISSN: 2040-3364
The potential of a given π-conjugated organic molecule in an organic semiconductor device is highly dependent on molecular packing, as it strongly influences the charge-carrier mobility of the material. Such solid-state packing is sensitive to subtle differences in their intermolecular interactions and is challenging to predict. Chirality of the organic molecule adds an additional element of complexity to intuitive packing prediction. Here we use crystal structure prediction to explore the lattice-energy landscape of a potential chiral organic semiconductor, helicene. We reproduce the experimentally observed enantiopure crystal structure and explain the absence of an experimentally observed racemate structure. By exploring how the hole and electron-mobility varies across the energy–structure–function landscape for helicene, we find that an energetically favourable and frequently occurring packing motif is particularly promising for electron-mobility, with a highest calculated mobility of 2.9 cm2 V−1 s−1 (assuming a reorganization energy of 0.46 eV). We also calculate relatively high hole-mobility in some structures, with a highest calculated mobility of 2.0 cm2 V−1 s−1 found for chains of helicenes packed in a herringbone fashion. Neither the energetically favourable nor high charge-carrier mobility packing motifs are intuitively obvious, and this demonstrates the utility of our approach to computationally explore the energy–structure–function landscape for organic semiconductors. Our work demonstrates a route for the use of computational simulations to aid in the design of new molecules for organic electronics, through the a priori prediction of their likely solid-state form and properties.
Miklitz M, Jiang S, Clowes R, et al., 2017, Computational screening of porous organic molecules for xenon/krypton separation, Journal of Physical Chemistry C, Vol: 121, Pages: 15211-15222, ISSN: 1932-7447
We performed a computational screening of previously reported porous molecular materials, including porous organic cages, cucurbiturils, cyclodextrins, and cryptophanes, for Xe/Kr separation. Our approach for rapid screening through analysis of single host molecules, rather than the solid state structure of the materials, is evaluated. We use a set of tools including in-house software for structural evaluations, electronic structure calculations for guest binding energies, and molecular dynamics and metadynamics simulations to study the effect of the hosts’ flexibility upon guest diffusion. Our final results confirm that the CC3 cage molecule, previously reported as high performing for Xe/Kr separation, is the most promising of this class of materials reported to date. The Noria molecule was also found to be promising, and we therefore synthesized two related Noria molecules and tested their performance for Xe/Kr separation in the laboratory.
Hasell T, Little MA, Chong SY, et al., 2017, Chirality as a tool for function in porous organic cages, Nanoscale, Vol: 9, Pages: 6783-6790, ISSN: 2040-3364
The control of solid state assembly for porous organic cages is more challenging than for extended frameworks, such as metal–organic frameworks. Chiral recognition is one approach to achieving this control. Here we investigate chiral analogues of cages that were previously studied as racemates. We show that chiral cages can be produced directly from chiral precursors or by separating racemic cages by co-crystallisation with a second chiral cage, opening up a route to producing chiral cages from achiral precursors. These chiral cages can be cocrystallized in a modular, ‘isoreticular’ fashion, thus modifying porosity, although some chiral pairings require a specific solvent to direct the crystal into the desired packing mode. Certain cages are shown to interconvert chirality in solution, and the steric factors governing this behavior are explored both by experiment and by computational modelling.
Evans JD, Jelfs KE, Day GM, et al., 2017, Application of computational methods to the design and characterisation of porous molecular materials, Chemical Society Reviews, Vol: 46, Pages: 3286-3301, ISSN: 1460-4744
Composed from discrete units, porous molecular materials (PMMs) possess unique properties not observed for conventional, extended, solids, such as solution processibility and permanent porosity in the liquid phase. However, identifying the origin of porosity is not a trivial process, especially for amorphous or liquid phases. Furthermore, the assembly of molecular components is typically governed by a subtle balance of weak intermolecular forces that makes structure prediction challenging. Accordingly, in this review we canvass the crucial role of molecular simulations in the characterisation and design of PMMs. We will outline strategies for modelling porosity in crystalline, amorphous and liquid phases and also describe the state-of-the-art methods used for high-throughput screening of large datasets to identify materials that exhibit novel performance characteristics.
We define a nomenclature for the classification of porous organic cage molecules, enumerating the 20 most probable topologies, 12 of which have been synthetically realised to date. We then discuss the computational challenges encountered when trying to predict the most likely topological outcomes from dynamic covalent chemistry (DCC) reactions of organic building blocks. This allows us to explore the extent to which comparing the internal energies of possible reaction outcomes is successful in predicting the topology for a series of 10 different building block combinations.
Song Q, Liu TY, Jelfs KE, et al., 2017, Advanced Microporous Membranes for Molecular Separations, British Zeolite Association 40th Annual Meeting
Slater AG, Little MA, Pulido A, et al., 2016, Reticular synthesis of porous molecular 1D nanotubes and 3D networks, Nature Chemistry, Vol: 9, Pages: 17-25, ISSN: 1755-4349
Synthetic control over pore size and pore connectivity is the crowning achievement for porous metal-organic frameworks (MOFs). The same level of control has not been achieved for molecular crystals, which are not defined by strong, directional intermolecular coordination bonds. Hence, molecular crystallization is inherently less controllable than framework crystallization, and there are fewer examples of 'reticular synthesis', in which multiple building blocks can be assembled according to a common assembly motif. Here we apply a chiral recognition strategy to a new family of tubular covalent cages to create both 1D porous nanotubes and 3D diamondoid pillared porous networks. The diamondoid networks are analogous to MOFs prepared from tetrahedral metal nodes and linear ditopic organic linkers. The crystal structures can be rationalized by computational lattice-energy searches, which provide an in silico screening method to evaluate candidate molecular building blocks. These results are a blueprint for applying the 'node and strut' principles of reticular synthesis to molecular crystals.
By synthesizing derivatives of a trans-1,2-diaminocyclohexane precursor, three new functionalized porous organic cages were prepared with different chemical functionalities on the cage periphery. The introduction of twelve methyl groups (CC16) resulted in frustration of the cage packing mode, which more than doubled the surface area compared to the parent cage, CC3. The analogous installation of twelve hydroxyl groups provided an imine cage (CC17) that combines permanent porosity with the potential for post-synthetic modification of the cage exterior. Finally, the incorporation of bulky dihydroethanoanthracene groups was found to direct self-assembly towards the formation of a larger [8+12] cage, rather than the expected [4+6], cage molecule (CC18). However, CC18 was found to be non-porous, most likely due to cage collapse upon desolvation.
Holden D, Chong SY, Chen L, et al., 2016, Understanding static, dynamic and cooperative porosity in molecular materials, Chemical Science, Vol: 7, Pages: 4875-4879, ISSN: 2041-6539
The practical adsorption properties of molecular porous solids can be dominated by dynamic flexibility but these effects are still poorly understood. Here, we combine molecular simulations and experiments to rationalize the adsorption behavior of a flexible porous organic cage.
Zwijnenburg MA, Berardo E, Peveler WJ, et al., 2016, Amine molecular cages as supramolecular fluorescent explosive sensors: a computational perspective, Journal of Physical Chemistry B, Vol: 120, Pages: 5063-5072, ISSN: 1520-6106
We investigate using a computational approach the physical and chemical processes underlying the application of organic (macro)molecules as fluorescence quenching sensors for explosives sensing. We concentrate on the use of amine molecular cages to sense nitroaromatic analytes, such as picric acid and 2,4-dinitrophenol, through fluorescence quenching. Our observations for this model system hold for many related systems. We consider the different possible mechanisms of fluorescence quenching: Förster resonance energy transfer, Dexter energy transfer and photoinduced electron transfer, and show that in the case of our model system, the fluorescence quenching is driven by the latter and involves stable supramolecular sensor–analyte host–guest complexes. Furthermore, we demonstrate that the experimentally observed selectivity of amine molecular cages for different explosives can be explained by the stability of these host–guest complexes and discuss how this is related to the geometry of the binding site in the sensor. Finally, we discuss what our observations mean for explosive sensing by fluorescence quenching in general and how this can help in future rational design of new supramolecular detection systems.
Jimenez-Solomon M, Song Q, Jelfs K, et al., 2016, Polymer nanofilms with enhanced microporosity by interfacial polymerisation, Nature Materials, Vol: 15, Pages: 760-767, ISSN: 1476-4660
Highly permeable and selective membranes are desirable for energy-efficient gas and liquid separations.Microporous organic polymers have attracted significant attention in this respect owing to their highporosity, permeability, and molecular selectivity. However, it remains challenging to fabricate selectivepolymer membranes with controlled microporosity which are stable in solvents. Here we report a newapproach to designing crosslinked, rigid polymer nanofilms with enhanced microporosity bymanipulating the molecular structure. Ultra-thin polyarylate nanofilms with thickness down to 20 nmwere formed in-situ by interfacial polymerisation. Enhanced microporosity and higher interconnectivityof intermolecular network voids, as rationalised by molecular simulations, are achieved by utilisingcontorted monomers for the interfacial polymerisation. Composite membranes comprising polyarylatenanofilms with enhanced microporosity fabricated in-situ on crosslinked polyimide ultrafiltrationmembranes show outstanding separation performance in organic solvents, with up to two orders ofmagnitude higher solvent permeance than membranes fabricated with nanofilms made from noncontortedplanar monomers.
The porosity of a glass formed by melt-quenching a metal-organic framework, has been characterized by positron annihilation lifetime spectroscopy. The results reveal porosity intermediate between the related open and dense crystalline frameworks ZIF-4 and ZIF-zni. A structural model for the glass was constructed using an amorphous polymerization algorithm, providing additional insight into the gas-inaccessible nature of porosity and the possible applications of hybrid glasses.
Hasell T, Miklitz M, Stephenson A, et al., 2016, Porous organic cages for sulfur hexafluoride separation., Journal of the American Chemical Society, Vol: 138, Pages: 1653-1659, ISSN: 1520-5126
A series of porous organic cages is examined for the selective adsorption of sulphur hexafluoride (SF6) over nitrogen. Despite lacking any metal sites, a porous cage, CC3, shows the highest SF6/N2 selectivity reported for any material at ambient temperature and pressure, which translates to real separations in a gas breakthrough column. The SF6 uptake of these materials is considerably higher than would be expected from the static pore structures. The location of SF6 within these materials is elucidated by x-ray crystallography, and it is shown that cooperative diffusion and structural rearrangements in these molecular crystals can rationalize their superior SF6/N2 selectivity.
Jimenez-Solomon MF, Song Q, Jelfs KE, et al., 2016, Polymer nanofilms with enhanced microporosity by interfacial polymerisation for molecular separations
Manurung R, Holden D, Miklitz M, et al., 2015, Tunable porosity through cooperative diffusion in amulticomponent porous molecular crystal, Journal of Physical Chemistry C, Vol: 119, Pages: 22577-22586, ISSN: 1932-7455
A combination of different molecular simulation techniques was used to begin to uncover the mechanism behind the compositional tuning of gas sorption behaviour in a multicomponent porous molecular crystal, CC1.CC3n.CC41-n, where 0 < n < 1. Gas access to formally occluded voids was found to be allowed through a cooperative diffusion mechanism that requires the presence of the guest for the channel to briefly open. Molecular dynamics simulations and dynamic void analysis suggest two putative diffusion mechanisms. We propose that the gas diffusion is controlled by the cage vertices that surround the void, with the slightly smaller and more mobile cyclopentane vertices in CC4 allowing more facile nitrogen diffusion than the cyclohexane vertices in CC3. A combination of sorption simulations, void analysis and statistical calculations suggest the diffusion mechanism may rely upon the presence of two CC4 molecules adjacent to the occluded voids.
Jelfs KE, Santolini V, Tribello GA, 2015, Predicting solvent effects on the structure of porous organic molecules, Chemical Communications, Vol: 51, Pages: 15542-15545, ISSN: 1364-548X
A computational approach for the prediction of the open, metastable, conformations of porous organic molecules in the presence of solvent is developed.
Little MA, Briggs ME, Jones JTA, et al., 2015, Trapping virtual pores by crystal retro-engineering, NATURE CHEMISTRY, Vol: 7, Pages: 153-159, ISSN: 1755-4330
Solomon MFJ, Song Q, Munoz-Ibanez M, et al., 2015, TFC membranes with intrinsic microporosity by interfacial polymerization for organic solvent nanofiltration, Pages: 679-680
Chen L, Reiss PS, Chong SY, et al., 2014, Separation of rare gases and chiral molecules by selective binding in porous organic cages, NATURE MATERIALS, Vol: 13, Pages: 954-960, ISSN: 1476-1122
Holden D, Jelfs KE, Trewin A, et al., 2014, Gas Diffusion in a Porous Organic Cage: Analysis of Dynamic Pore Connectivity Using Molecular Dynamics Simulations, JOURNAL OF PHYSICAL CHEMISTRY C, Vol: 118, Pages: 12734-12743, ISSN: 1932-7447
Liu M, Little MA, Jelfs KE, et al., 2014, Acid- and Base-Stable Porous Organic Cages: Shape Persistence and pH Stability via Post-synthetic "Tying" of a Flexible Amine Cage, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 136, Pages: 7583-7586, ISSN: 0002-7863
Warren JE, Perkins CG, Jelfs KE, et al., 2014, Shape Selectivity by Guest- Driven Restructuring of a Porous Material, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, Vol: 53, Pages: 4592-4596, ISSN: 1433-7851
Boldrin P, Rosseinsky MJ, Perkins CG, et al., 2014, METAL-ORGANIC FRAMEWORKS, WO 2014/033481 A2
The present invention relates to compounds capable of forming metal-organic frameworks (MOFs), particularly f-block metal MOFs which selectively sorb one component (e.g. para-xylene) from a mixture of components (e.g. m-/p-xylene mixture). The invention also relates to methods of producing and using said compounds
Hasell T, Culshaw JL, Chong SY, et al., 2014, Controlling the Crystallization of Porous Organic Cages: Molecular Analogs of Isoreticular Frameworks Using Shape-Specific Directing Solvents, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 136, Pages: 1438-1448, ISSN: 0002-7863
Pyzer-Knapp EO, Thompson HPG, Schiffmann F, et al., 2014, Predicted crystal energy landscapes of porous organic cages, Chemical Science, Vol: 5, Pages: 2235-2245, ISSN: 2041-6520
In principle, the development of computational methods for structure and property prediction offers the potential for the in silico design of functional materials. Here, we evaluate the crystal energy landscapes of a series of porous organic cages, for which small changes in chemical structure lead to completely different crystal packing arrangements and, hence, porosity. The differences in crystal packing are not intuitively obvious from the molecular structure, and hence qualitative approaches to crystal engineering have limited scope for designing new materials. We find that the crystal structures and the resulting porosity of these molecular crystals can generally be predicted in silico, such that computational screening of similar compounds should be possible. The computational predictability of organic cage crystal packing is demonstrated by the subsequent discovery, during screening of crystallisation conditions, of the lowest energy predicted structure for one of the cages. This journal is © the Partner Organisations 2014.
Jiang S, Jelfs KE, Holden D, et al., 2013, Molecular Dynamics Simulations of Gas Selectivity in Amorphous Porous Molecular Solids, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 135, Pages: 17818-17830, ISSN: 0002-7863
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