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Wade J, Salerno F, Kilbride RC, Kim DK, Schmidt JA, Smith JA, LeBlanc LM, Wolpert EH, Adeleke AA, Johnson ER, Nelson J, Mori T, Jelfs KE, Heutz S, Fuchter MJ. Controlling anisotropic properties by manipulating the orientation of chiral small molecules. Nat Chem 2022; 14:1383-1389. [PMID: 36302869 DOI: 10.1038/s41557-022-01044-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Accepted: 08/22/2022] [Indexed: 01/04/2023]
Abstract
Chiral π-conjugated molecules bring new functionality to technological applications and represent an exciting, rapidly expanding area of research. Their functional properties, such as the absorption and emission of circularly polarized light or the transport of spin-polarized electrons, are highly anisotropic. As a result, the orientation of chiral molecules critically determines the functionality and efficiency of chiral devices. Here we present a strategy to control the orientation of a small chiral molecule (2,2'-dicyano[6]helicene) by the use of organic and inorganic templating layers. Such templating layers can either force 2,2'-dicyano[6]helicene to adopt a face-on orientation and self-assemble into upright supramolecular columns oriented with their helical axis perpendicular to the substrate, or an edge-on orientation with parallel-lying supramolecular columns. Through such control, we show that low- and high-energy chiroptical responses can be independently 'turned on' or 'turned off'. The templating methodologies described here provide a simple way to engineer orientational control and, by association, anisotropic functional properties of chiral molecular systems for a range of emerging technologies.
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Affiliation(s)
- Jessica Wade
- Department of Materials and London Centre for Nanotechnology, Imperial College London, London, UK.
- Centre for Processable Electronics, Imperial College London, London, UK.
| | - Francesco Salerno
- Centre for Processable Electronics, Imperial College London, London, UK
- Department of Chemistry and Molecular Sciences Research Hub, Imperial College London, London, UK
| | - Rachel C Kilbride
- Department of Physics and Astronomy, The University of Sheffield, Sheffield, UK
| | - Dong Kuk Kim
- Department of Materials and London Centre for Nanotechnology, Imperial College London, London, UK
- Centre for Processable Electronics, Imperial College London, London, UK
| | - Julia A Schmidt
- Department of Chemistry and Molecular Sciences Research Hub, Imperial College London, London, UK
| | - Joel A Smith
- Department of Physics, Clarendon Laboratory, University of Oxford, Oxford, UK
| | - Luc M LeBlanc
- Department of Chemistry, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Emma H Wolpert
- Department of Chemistry and Molecular Sciences Research Hub, Imperial College London, London, UK
| | - Adebayo A Adeleke
- Department of Chemistry, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Erin R Johnson
- Department of Chemistry, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Jenny Nelson
- Centre for Processable Electronics, Imperial College London, London, UK
- Department of Physics, Imperial College London, London, UK
| | - Tadashi Mori
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita, Japan
| | - Kim E Jelfs
- Centre for Processable Electronics, Imperial College London, London, UK
- Department of Chemistry and Molecular Sciences Research Hub, Imperial College London, London, UK
| | - Sandrine Heutz
- Department of Materials and London Centre for Nanotechnology, Imperial College London, London, UK
- Centre for Processable Electronics, Imperial College London, London, UK
| | - Matthew J Fuchter
- Centre for Processable Electronics, Imperial College London, London, UK.
- Department of Chemistry and Molecular Sciences Research Hub, Imperial College London, London, UK.
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Gale JD, LeBlanc LM, Spackman PR, Silvestri A, Raiteri P. A Universal Force Field for Materials, Periodic GFN-FF: Implementation and Examination. J Chem Theory Comput 2021; 17:7827-7849. [PMID: 34735764 DOI: 10.1021/acs.jctc.1c00832] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
In this study, the adaption of the recently published molecular GFN-FF for periodic boundary conditions (pGFN-FF) is described through the use of neighbor lists combined with appropriate charge sums to handle any dimensionality from 1D polymers to 2D surfaces and 3D solids. Numerical integration over the Brillouin zone for the calculation of π bond orders of periodic fragments is also included. Aside from adapting the GFN-FF method to handle periodicity, improvements to the method are proposed in regard to the calculation of topological charges through the inclusion of a screened Coulomb term that leads to more physical charges and avoids a number of pathological cases. Short-range damping of three-body dispersion is also included to avoid collapse of some structures. Analytic second derivatives are also formulated with respect to both Cartesian and strain variables, including prescreening of terms to accelerate the dispersion/coordination number contribution to the Hessian. The modified pGFN-FF scheme is then applied to a wide range of different materials in order to examine how well this universal model performs.
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Affiliation(s)
- Julian D Gale
- Curtin Institute for Computation, School of Molecular and Life Sciences, Curtin University, PO Box U1987, Perth, Western Australia 6845, Australia
| | - Luc M LeBlanc
- Curtin Institute for Computation, School of Molecular and Life Sciences, Curtin University, PO Box U1987, Perth, Western Australia 6845, Australia
| | - Peter R Spackman
- Curtin Institute for Computation, School of Molecular and Life Sciences, Curtin University, PO Box U1987, Perth, Western Australia 6845, Australia
| | - Alessandro Silvestri
- Curtin Institute for Computation, School of Molecular and Life Sciences, Curtin University, PO Box U1987, Perth, Western Australia 6845, Australia
| | - Paolo Raiteri
- Curtin Institute for Computation, School of Molecular and Life Sciences, Curtin University, PO Box U1987, Perth, Western Australia 6845, Australia
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Abstract
A recent study by Tawfik et al. [ Phys. Rev. Mater. 2018, 2, 034005] found that few density functionals, none of which are asymptotic pairwise dispersion methods, describe the geometry and binding of layered materials accurately. Here, we show that the exchange-hole dipole moment (XDM) dispersion model attains excellent results for graphite, hexagonal BN, and transition-metal dichalcogenides. Contrary to what has been argued, successful modeling of layered materials does not necessitate meta-GGA exchange, nonlocal correlation functionals, or the inclusion of three-body dispersion terms. Rather, a GGA functional, combined with a simple asymptotic pairwise dispersion correction, can be reliably used, provided that it properly accounts for the geometric dependence of the dispersion coefficients. The overwhelming contribution to the variation of the pairwise dispersion coefficients comes from the immediate vicinity of an atom and is already present for single layers. Longer-range and interlayer effects are examined in detail for graphite.
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Affiliation(s)
- A Otero-de-la-Roza
- Departamento de Química Física y Analítica, Facultad de Química, Universidad de Oviedo, 33006 Oviedo, Spain
| | - Luc M LeBlanc
- Department of Chemistry, Dalhousie University, 6274 Coburg Road, Halifax, Nova Scotia B3H 4R2, Canada
| | - Erin R Johnson
- Department of Chemistry, Dalhousie University, 6274 Coburg Road, Halifax, Nova Scotia B3H 4R2, Canada
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Abstract
“Many-body” dispersion can refer to two distinct phenomena, here termed electronic and atomic many-body effects, both of which cause the dispersion energy to be non-additive.
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Affiliation(s)
- A. Otero-de-la-Roza
- Departamento de Química Física y Analítica and MALTA-Consolider Team
- Facultad de Química
- Universidad de Oviedo
- 33006 Oviedo
- Spain
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Noël JA, LeBlanc LM, Patterson DS, Kreplak L, Fleischauer MD, Johnson ER, White MA. Clusters in Liquid Fatty Acids: Structure and Role in Nucleation. J Phys Chem B 2019; 123:7043-7054. [PMID: 31322886 DOI: 10.1021/acs.jpcb.9b05017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Saturated fatty acids are used in many consumer products and have considerable promise as phase change materials for thermal energy storage, in part because they crystallize with minimal supercooling. The latter property correlates with the existence of molecular clusters in the liquid; when heated above a threshold temperature, clusters do not immediately re-form on cooling, and supercooling results. Raman spectroscopy, density functional theory calculations, and small-angle X-ray scattering were used to reveal the size, structure, and temperature dependence of the clusters. We found that the liquid phases of fatty acids contain some ordering at all temperatures, with the molecules showing, on average, short-range alignment along their long axes. At temperatures below the threshold temperature for increased susceptibility to supercooling, clusters of more highly ordered fatty acid dimers, several hundred molecules in size, exist in the liquid. Within these clusters, the alkyl chains of the fatty acid dimers are essentially completely inserted between the alkyl chains of their longitudinal neighbors. Above the threshold temperature, fatty acid clusters are smaller in size and number. We explored how the fatty acid clusters promote bulk crystallization and show quantitatively that their presence reduces the energy barrier to crystal growth, likely by a particle-attachment-type mechanism.
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Affiliation(s)
| | | | - Daphne Sunita Patterson
- National Research Council-Nanotechnology Research Centre , Edmonton , Alberta T6G 2M9 , Canada
| | | | - Michael D Fleischauer
- National Research Council-Nanotechnology Research Centre , Edmonton , Alberta T6G 2M9 , Canada.,Department of Physics , University of Alberta , Edmonton , Alberta T6G 2E1 , Canada
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Otero-de-la-Roza A, LeBlanc LM, Johnson ER. Dispersion XDM with Hybrid Functionals: Delocalization Error and Halogen Bonding in Molecular Crystals. J Chem Theory Comput 2019; 15:4933-4944. [DOI: 10.1021/acs.jctc.9b00550] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- A. Otero-de-la-Roza
- Departamento de Química Física y Analítica, Facultad de Química, Universidad de Oviedo, 33006 Oviedo, Spain
| | - Luc M. LeBlanc
- Department of Chemistry, Dalhousie University, 6274 Coburg Road, Halifax, Nova Scotia B3H 4R2, Canada
| | - Erin R. Johnson
- Department of Chemistry, Dalhousie University, 6274 Coburg Road, Halifax, Nova Scotia B3H 4R2, Canada
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Abstract
Composite methods employing dispersion-corrected DFT consistently identify experimentally isolated polymorphs as the lowest-energy crystal structures of common APIs.
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Affiliation(s)
- Luc M. LeBlanc
- Department of Chemistry
- Dalhousie University
- Halifax
- Canada
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LeBlanc LM, Dale SG, Taylor CR, Becke AD, Day GM, Johnson ER. Pervasive Delocalisation Error Causes Spurious Proton Transfer in Organic Acid-Base Co-Crystals. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201809381] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Luc M. LeBlanc
- Department of Chemistry; Dalhousie University; P.O. Box 15000, 6274 Coburg Rd Halifax Nova Scotia B3H 4R2 Canada
| | - Stephen G. Dale
- Department of Chemistry; Dalhousie University; P.O. Box 15000, 6274 Coburg Rd Halifax Nova Scotia B3H 4R2 Canada
| | | | - Axel D. Becke
- Department of Chemistry; Dalhousie University; P.O. Box 15000, 6274 Coburg Rd Halifax Nova Scotia B3H 4R2 Canada
| | - Graeme M. Day
- School of Chemistry; University of Southampton, Highfield; Southampton SO17 1BJ UK
| | - Erin R. Johnson
- Department of Chemistry; Dalhousie University; P.O. Box 15000, 6274 Coburg Rd Halifax Nova Scotia B3H 4R2 Canada
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LeBlanc LM, Weatherby JA, Otero-de-la-Roza A, Johnson ER. Non-Covalent Interactions in Molecular Crystals: Exploring the Accuracy of the Exchange-Hole Dipole Moment Model with Local Orbitals. J Chem Theory Comput 2018; 14:5715-5724. [DOI: 10.1021/acs.jctc.8b00797] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Luc M. LeBlanc
- Department of Chemistry, Dalhousie University, 6274 Coburg Road, Halifax, Nova Scotia B3H 4R2, Canada
| | - Joseph A. Weatherby
- Department of Chemistry, Dalhousie University, 6274 Coburg Road, Halifax, Nova Scotia B3H 4R2, Canada
| | - Alberto Otero-de-la-Roza
- Departamento de Quı́mica Fı́sica y Analı́tica, Facultad de Quı́mica, Universidad de Oviedo, 33006 Oviedo, Spain
| | - Erin R. Johnson
- Department of Chemistry, Dalhousie University, 6274 Coburg Road, Halifax, Nova Scotia B3H 4R2, Canada
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LeBlanc LM, Dale SG, Taylor CR, Becke AD, Day GM, Johnson ER. Pervasive Delocalisation Error Causes Spurious Proton Transfer in Organic Acid-Base Co-Crystals. Angew Chem Int Ed Engl 2018; 57:14906-14910. [PMID: 30248221 DOI: 10.1002/anie.201809381] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Indexed: 11/12/2022]
Abstract
Dispersion-corrected density-functional theory (DFT-D) methods have become the workhorse of many computational protocols for molecular crystal structure prediction due to their efficiency and convenience. However, certain limitations of DFT, such as delocalisation error, are often overlooked or are too expensive to remedy in solid-state applications. This error can lead to artificial stabilisation of charge transfer and, in this work, it is found to affect the correct identification of the protonation site in multicomponent acid-base crystals. As such, commonly used DFT-D methods cannot be applied with any reliability to the study of acid-base co-crystals or salts, while hybrid functionals remain too restrictive for routine use. This presents an impetus for the development of new functionals with reduced delocalisation error for solid-state applications; the structures studied herein constitute an excellent benchmark for this purpose.
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Affiliation(s)
- Luc M LeBlanc
- Department of Chemistry, Dalhousie University, P.O. Box 15000, 6274 Coburg Rd, Halifax, Nova Scotia, B3H 4R2, Canada
| | - Stephen G Dale
- Department of Chemistry, Dalhousie University, P.O. Box 15000, 6274 Coburg Rd, Halifax, Nova Scotia, B3H 4R2, Canada
| | - Christopher R Taylor
- School of Chemistry, University of Southampton, Highfield, Southampton, SO17 1BJ, UK
| | - Axel D Becke
- Department of Chemistry, Dalhousie University, P.O. Box 15000, 6274 Coburg Rd, Halifax, Nova Scotia, B3H 4R2, Canada
| | - Graeme M Day
- School of Chemistry, University of Southampton, Highfield, Southampton, SO17 1BJ, UK
| | - Erin R Johnson
- Department of Chemistry, Dalhousie University, P.O. Box 15000, 6274 Coburg Rd, Halifax, Nova Scotia, B3H 4R2, Canada
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Rice B, LeBlanc LM, Otero-de-la-Roza A, Fuchter MJ, Johnson ER, Nelson J, Jelfs KE. Correction: A computational exploration of the crystal energy and charge-carrier mobility landscapes of the chiral [6]helicene molecule. Nanoscale 2018; 10:9410. [PMID: 29722420 DOI: 10.1039/c8nr90093k] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Correction for 'A computational exploration of the crystal energy and charge-carrier mobility landscapes of the chiral [6]helicene molecule' by Beth Rice et al., Nanoscale, 2018, 10, 1865-1876.
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Affiliation(s)
- Beth Rice
- Department of Physics, Imperial College London, South Kensington, London, SW7 2AZ, UK
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12
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Abstract
Molecular crystal structure prediction (CSP) requires evaluating differences in lattice energy between candidate crystal structures accurately and efficiently. In this work, we explore and compare several low-cost alternatives to dispersion-corrected density-functional theory (DFT) in the plane-waves/pseudopotential approximation, the most accurate and general approach used for CSP at present. Three types of low-cost methods are considered: DFT with a small basis set of finite-support numerical orbitals (the SIESTA method), dispersion-corrected Gaussian small or minimal-basis-set Hartree-Fock and DFT with additional empirical corrections (HF-3c and PBEh-3c), and self-consistent-charge dispersion-corrected density-functional tight binding (SCC-DFTB3-D3). In addition, we study the performance of composite methods that comprise a geometry optimization using a low-cost approach followed by a single-point calculation using the accurate but comparatively expensive B86bPBE-XDM functional. All methods were tested for their abilities to produce absolute lattice energies, relative lattice energies, and crystal geometries. We show that assessing various methods by their ability to produce absolute lattice energies can be misleading and that relative lattice energies are a much better indicator of performance in CSP. The EE14 set of relative solubilities of homochiral and heterochiral chiral crystals is proposed for relative lattice-energy benchmarking. Our results show that PBE-D2 plus a DZP basis set of numerical orbitals coupled with a final B86bPBE-XDM single-point calculation gives excellent performance at a fraction of the cost of a full B86bPBE-XDM calculation, although the results are sensitive to the particular details of the computational protocol. The B86bPBE-XDM//PBE-D2/DZP method was subsequently tested in a practical CSP application from our recent work on the crystal structure of the enantiopure and racemate forms of 1-aza[6]helicene, a chiral organic semiconductor. Our results show that this multilevel method is able to correctly reproduce the energy ranking of both crystal forms.
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Affiliation(s)
- Luc M LeBlanc
- Department of Chemistry , Dalhousie University , 6274 Coburg Road , P.O. Box 15000, Halifax , Nova Scotia , Canada B3H 4R2
| | - Alberto Otero-de-la-Roza
- Department of Chemistry , University of British Columbia, Okanagan , 3247 University Way , Kelowna , British Columbia , Canada V1V 1V7
| | - Erin R Johnson
- Department of Chemistry , Dalhousie University , 6274 Coburg Road , P.O. Box 15000, Halifax , Nova Scotia , Canada B3H 4R2
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Rice B, LeBlanc LM, Otero-de-la-Roza A, Fuchter MJ, Johnson ER, Nelson J, Jelfs KE. A computational exploration of the crystal energy and charge-carrier mobility landscapes of the chiral [6]helicene molecule. Nanoscale 2018; 10:1865-1876. [PMID: 29313040 DOI: 10.1039/c7nr08890f] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
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, [6]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 [6]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.
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Affiliation(s)
- Beth Rice
- Department of Physics, Imperial College London, South Kensington, London, SW7 2AZ, UK and Centre for Plastic Electronics, Imperial College London, South Kensington, London, SW7 2AZ, UK.
| | - Luc M LeBlanc
- Department of Chemistry, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
| | - Alberto Otero-de-la-Roza
- Department of Chemistry, University of British Columbia, Okanagan, 3247 University Way, Kelowna, British Columbia V1V 1V7, Canada
| | - Matthew J Fuchter
- Centre for Plastic Electronics, Imperial College London, South Kensington, London, SW7 2AZ, UK. and Department of Chemistry, Imperial College London, South Kensington, London, SW7 2AZ, UK
| | - Erin R Johnson
- Department of Chemistry, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
| | - Jenny Nelson
- Department of Physics, Imperial College London, South Kensington, London, SW7 2AZ, UK and Centre for Plastic Electronics, Imperial College London, South Kensington, London, SW7 2AZ, UK.
| | - Kim E Jelfs
- Centre for Plastic Electronics, Imperial College London, South Kensington, London, SW7 2AZ, UK. and Department of Chemistry, Imperial College London, South Kensington, London, SW7 2AZ, UK
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LeBlanc LM, Powers SW, Grossert JS, White RL. Competing fragmentation processes of β-substituted propanoate ions upon collision-induced dissociation. Rapid Commun Mass Spectrom 2016; 30:2133-2144. [PMID: 27476993 DOI: 10.1002/rcm.7699] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Revised: 07/22/2016] [Accepted: 07/22/2016] [Indexed: 06/06/2023]
Abstract
RATIONALE When subjected to collisional activation, gas-phase carboxylate ions typically undergo decarboxylation. However, alternative fragmentation processes dominate when the carboxylate group is located within certain structural motifs. In this work, the fragmentation processes of β-substituted carboxylate ions are characterized to improve correlations between reactivity and structure. METHODS Mass spectra were collected using both ion trap and triple quadrupole mass spectrometers operating in the negative ion mode; collision-induced dissociation (CID) of ions was used to study the relationship between product ions and the structures of their precursor ions. Quantum mechanical computations were performed on a full range of reaction geometries at the MP2/6-311++G(2d,p)//B3LYP/6-31++G(2d,p) level of theory. RESULTS For a series of β-substituted carboxylate ions, a product ion corresponding to the anion of the β-substituent was obtained upon CID. Detailed computations indicated that decarboxylative elimination and at least one other fragmentation mechanism had feasible energetics for the formation of substituent anions differing in their gas-phase basicities. Predicted energetics for anti- and synperiplanar alignments in the transition structures for decarboxylative elimination correlated with the positions of crossover points in breakdown curves acquired for conformationally constrained ions. CONCLUSIONS The feasibility of more than one mechanism was established for the fragmentation of β-substituted propanoates. The contribution of each mechanistic pathway to the formation of the substituent anion was influenced by structural variations and conformational constraints, but mostly depended on the nature of the substituent. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Luc M LeBlanc
- Department of Chemistry, Dalhousie University, 6274 Coburg Road, PO Box 15000, Halifax, Nova Scotia, Canada, B3H 4R2
| | - Sean W Powers
- Department of Chemistry, Dalhousie University, 6274 Coburg Road, PO Box 15000, Halifax, Nova Scotia, Canada, B3H 4R2
| | - J Stuart Grossert
- Department of Chemistry, Dalhousie University, 6274 Coburg Road, PO Box 15000, Halifax, Nova Scotia, Canada, B3H 4R2
| | - Robert L White
- Department of Chemistry, Dalhousie University, 6274 Coburg Road, PO Box 15000, Halifax, Nova Scotia, Canada, B3H 4R2.
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LeBlanc LM, Crowell AMJ, Grossert JS, White RL. Phenyl group participation in rearrangements during collision-induced dissociation of deprotonated phenoxyacetic acid. Rapid Commun Mass Spectrom 2015; 29:2293-2301. [PMID: 26522323 DOI: 10.1002/rcm.7395] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Revised: 08/11/2015] [Accepted: 09/10/2015] [Indexed: 06/05/2023]
Abstract
RATIONALE The identification of trace constituents in biological and environmental samples is frequently based on the fragmentation patterns resulting from the collision-induced dissociation (CID) of gas-phase ions. Credible mechanistic characterization of fragmentation processes, including rearrangements, is required to make reliable assignments for structures of precursor and product ions. METHODS Mass spectra were collected using both ion trap and triple quadrupole mass spectrometers operating in the negative ion mode. Precursor ion scans and CID of ions generated in-source were used to establish precursor-product ion relationships. Density functional theory (DFT) computations were performed at the MP2/6-311++G(2d,p)//B3LYP/6-31++G(2d,p) level of theory. RESULTS Product ions at m/z 93 and 107 obtained upon CID of phenoxyacetate were attributed to phenoxide and o-methylphenoxide, respectively. An isotopic labeling experiment and computations showed that the phenoxide ion was formed by intramolecular displacement with formation of an α-lactone and also by a Smiles rearrangement. Rearrangement of phenoxyacetate via the ion-neutral complex formed in the α-lactone displacement pathway gave the isomeric o-hydroxyphenylacetate ion which yielded o-methylphenoxide upon decarboxylation. Computations provided feasible energetics for these pathways. CONCLUSIONS Previously unrecognized and energetically favorable rearrangements during the collision-induced fragmentation of phenoxyacetate have been characterized using isotopic labeling and DFT computations. Notably, the phenyl substituent plays an indispensable role in each rearrangement process resulting in multiple pathways for the fragmentation of phenoxyacetate.
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Affiliation(s)
- Luc M LeBlanc
- Department of Chemistry, Dalhousie University, 6274 Coburg Road, PO Box 15000, Halifax, Nova Scotia, B3H 4R2, Canada
| | - Andrew M J Crowell
- Department of Chemistry, Dalhousie University, 6274 Coburg Road, PO Box 15000, Halifax, Nova Scotia, B3H 4R2, Canada
| | - J Stuart Grossert
- Department of Chemistry, Dalhousie University, 6274 Coburg Road, PO Box 15000, Halifax, Nova Scotia, B3H 4R2, Canada
| | - Robert L White
- Department of Chemistry, Dalhousie University, 6274 Coburg Road, PO Box 15000, Halifax, Nova Scotia, B3H 4R2, Canada
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LeBlanc LM, Boyd RJ, Burnell DJ. Density Functional Theory Study of BF3-Mediated Additions of Enols and [(Trimethylsilyl)oxy]alkenes to an Oxyallyl Cation: Homologous Mukaiyama Reactions. J Phys Chem A 2015; 119:6714-22. [PMID: 26035071 DOI: 10.1021/acs.jpca.5b03003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The addition of enols and [(trimethylsilyl)oxy]alkenes, bearing methyl substituents at various positions, to a cyclic, BF3-complexed oxyallyl cation has been studied at the M06/6-311G(d)//B3LYP/6-31G(d) level of theory. The reactions with the [(trimethylsilyl)oxy]alkenes are homologous Mukaiyama reactions, which have not been examined computationally previously. In most instances a number of transition states were located, and the difference in energy between these transition states was not large, which pointed to low levels of diastereoselectivity in the reactions of the oxyallyl cation model compound. The lowest energy transition states were those with a synclinal geometry in which the alkene was positioned over the cyclic oxyallyl cation, and the relative orientation of the alkene and the oxyallyl cation was rationalized in terms of stabilizing intermolecular interactions, revealed by NBO analysis, between one or more fluorines of the complexed BF3 and hydrogens on the alkene moiety, and between the oxygen on the alkene and the π-system of the oxyallyl cation. Because, in most instances with these simple models, two or more transition states of relatively low energy were located, predictions of diastereoselectivity in more complex examples that are based on simple models cannot be recommended.
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Affiliation(s)
- Luc M LeBlanc
- Department of Chemistry, Dalhousie University, P.O. Box 15000, Halifax, Nova Scotia B3H 4R2, Canada
| | - Russell J Boyd
- Department of Chemistry, Dalhousie University, P.O. Box 15000, Halifax, Nova Scotia B3H 4R2, Canada
| | - D Jean Burnell
- Department of Chemistry, Dalhousie University, P.O. Box 15000, Halifax, Nova Scotia B3H 4R2, Canada
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Affiliation(s)
- Timothy D. R. Morgan
- Department of Chemistry, Dalhousie University,
P.O. Box 15000, Halifax, Nova Scotia B3H 4R2, Canada
| | - Luc M. LeBlanc
- Department of Chemistry, Dalhousie University,
P.O. Box 15000, Halifax, Nova Scotia B3H 4R2, Canada
| | - Giselle H. Ardagh
- Department of Chemistry, Dalhousie University,
P.O. Box 15000, Halifax, Nova Scotia B3H 4R2, Canada
| | - Russell J. Boyd
- Department of Chemistry, Dalhousie University,
P.O. Box 15000, Halifax, Nova Scotia B3H 4R2, Canada
| | - D. Jean Burnell
- Department of Chemistry, Dalhousie University,
P.O. Box 15000, Halifax, Nova Scotia B3H 4R2, Canada
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Morin P, Ferguson D, LeBlanc LM, Hébert MJG, Paré AF, Jean-François J, Surette ME, Touaibia M, Cuperlovic-Culf M. NMR metabolomics analysis of the effects of 5-lipoxygenase inhibitors on metabolism in glioblastomas. J Proteome Res 2013; 12:2165-76. [PMID: 23557402 DOI: 10.1021/pr400026q] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Changes across metabolic networks are emerging as an integral part of cancer development and progression. Increasing comprehension of the importance of metabolic processes as well as metabolites in cancer is stimulating exploration of novel, targeted treatment options. Arachidonic acid (AA) is a major component of phospholipids. Through the cascade catalyzed by cyclooxygenases and lipoxygenases, AA is also a precursor to cellular signaling molecules as well as molecules associated with a variety of diseases including cancer. 5-Lipoxygenase catalyzes the transformation of AA into leukotrienes (LT), important mediators of inflammation. High-throughput analysis of metabolic profiles was used to investigate the response of glioblastoma cell lines to treatment with 5-lipoxygenase inhibitors. Metabolic profiling of cells following drug treatment provides valuable information about the response and metabolic alterations induced by the drug action and give an indication of both on-target and off-target effects of drugs. Four different 5-lipoxygenase inhibitors and antioxidants were tested including zileuton, caffeic acid, and its analogues caffeic acid phenethyl ester and caffeic acid cyclohexethyl ester. A NMR approach identified metabolic signatures resulting from application of these compounds to glioblastoma cell lines, and metabolic data were used to develop a better understanding of the mode of action of these inhibitors.
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Affiliation(s)
- Pier Morin
- Department of Chemistry and Biochemistry, Université de Moncton, Moncton, Canada
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LeBlanc LM, Paré AF, Jean-François J, Hébert MJG, Surette ME, Touaibia M. Synthesis and antiradical/antioxidant activities of caffeic acid phenethyl ester and its related propionic, acetic, and benzoic acid analogues. Molecules 2012; 17:14637-50. [PMID: 23222926 PMCID: PMC6268051 DOI: 10.3390/molecules171214637] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2012] [Revised: 11/09/2012] [Accepted: 12/05/2012] [Indexed: 11/16/2022] Open
Abstract
Caffeic acid phenethyl ester (CAPE) is a bioactive component isolated from propolis. A series of CAPE analogues was synthesized and their antiradical/antioxidant effects analyzed. The effect of the presence of the double bond and of the conjugated system on the antioxidant effect is evaluated with the analogues obtained from 3-(3,4-dihydroxyphenyl) propanoic acid. Those obtained from 2-(3,4-dihydroxyphenyl) acetic acid and 3,4-dihydroxybenzoic acid allow the evaluation of the effect of the presence of two carbons between the carbonyl and aromatic system.
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Affiliation(s)
| | | | | | | | | | - Mohamed Touaibia
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +1-506-858-4493; Fax: +1-506-858-4541
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Boudreau LH, Maillet J, LeBlanc LM, Jean-François J, Touaibia M, Flamand N, Surette ME. Caffeic acid phenethyl ester and its amide analogue are potent inhibitors of leukotriene biosynthesis in human polymorphonuclear leukocytes. PLoS One 2012; 7:e31833. [PMID: 22347509 PMCID: PMC3276500 DOI: 10.1371/journal.pone.0031833] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2011] [Accepted: 01/12/2012] [Indexed: 01/20/2023] Open
Abstract
Background 5-lipoxygenase (5-LO) catalyses the transformation of arachidonic acid (AA) into leukotrienes (LTs), which are important lipid mediators of inflammation. LTs have been directly implicated in inflammatory diseases like asthma, atherosclerosis and rheumatoid arthritis; therefore inhibition of LT biosynthesis is a strategy for the treatment of these chronic diseases. Methodology/Principal Findings Analogues of caffeic acid, including the naturally-occurring caffeic acid phenethyl ester (CAPE), were synthesized and evaluated for their capacity to inhibit 5-LO and LTs biosynthesis in human polymorphonuclear leukocytes (PMNL) and whole blood. Anti-free radical and anti-oxidant activities of the compounds were also measured. Caffeic acid did not inhibit 5-LO activity or LT biosynthesis at concentrations up to 10 µM. CAPE inhibited 5-LO activity (IC50 0.13 µM, 95% CI 0.08–0.23 µM) more effectively than the clinically-approved 5-LO inhibitor zileuton (IC50 3.5 µM, 95% CI 2.3–5.4 µM). CAPE was also more effective than zileuton for the inhibition of LT biosynthesis in PMNL but the compounds were equipotent in whole blood. The activity of the amide analogue of CAPE was similar to that of zileuton. Inhibition of LT biosynthesis by CAPE was the result of the inhibition of 5-LO and of AA release. Caffeic acid, CAPE and its amide analog were free radical scavengers and antioxidants with IC50 values in the low µM range; however, the phenethyl moiety of CAPE was required for effective inhibition of 5-LO and LT biosynthesis. Conclusions CAPE is a potent LT biosynthesis inhibitor that blocks 5-LO activity and AA release. The CAPE structure can be used as a framework for the rational design of stable and potent inhibitors of LT biosynthesis.
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Affiliation(s)
- Luc H. Boudreau
- Département de chimie et biochimie, Université de Moncton, Moncton, Canada
- Centre de recherche de l'institut universitaire de cardiologie et de pneumologie de Québec (IUCPQ), Département de médecine, Faculté de médecine, Université Laval, Québec, Canada
| | - Jacques Maillet
- Département de chimie et biochimie, Université de Moncton, Moncton, Canada
| | - Luc M. LeBlanc
- Département de chimie et biochimie, Université de Moncton, Moncton, Canada
| | | | - Mohamed Touaibia
- Département de chimie et biochimie, Université de Moncton, Moncton, Canada
| | - Nicolas Flamand
- Centre de recherche de l'institut universitaire de cardiologie et de pneumologie de Québec (IUCPQ), Département de médecine, Faculté de médecine, Université Laval, Québec, Canada
| | - Marc E. Surette
- Département de chimie et biochimie, Université de Moncton, Moncton, Canada
- * E-mail:
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Nabavi DG, LeBlanc LM, Baxter B, Lee DH, Fox AJ, Lownie SP, Ferguson GG, Craen RA, Gelb AW, Lee TY. Monitoring cerebral perfusion after subarachnoid hemorrhage using CT. Neuroradiology 2001; 43:7-16. [PMID: 11214653 DOI: 10.1007/s002340000434] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The aim of this prospective study was to assess the feasibility and diagnostic relevance of repetitive dynamic (contrast-enhanced) CT measurements of cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) in the first 3 weeks after aneurysmal subarachnoid hemorrhage (SAH). In 15 patients with SAH, 59 dynamic CT studies including 944 regions of interest (ROI) were analyzed. The results were correlated with the clinical course and time after the event and the occurrence of vasospasm. Values for the entire series were 33.8+/-19.3 ml/100 g/min (CBF), 3.3+/-1.3 ml/100 g (CBV), and 7.3+/-3.9 s (MTT). Significant differences in CBF and CBV were found between ROI in grey and white matter, with time after the event, between patients with significant and absent or minor vasospasm, and between patients with and without a presumed vasospasm-related infarct.
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Affiliation(s)
- D G Nabavi
- Imaging Research Laboratories, John P. Robarts Research Institute, London, Ontario, Canada
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