1
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Knupe-Wolfgang P, Mahn B, Hilt G. The Application of Flow Chemistry for the Synthesis of Alkyl Sodium Compounds and Their Transformations with Weinreb Amides and Carboxylic Acids. Org Lett 2024. [PMID: 39141767 DOI: 10.1021/acs.orglett.4c02314] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/16/2024]
Abstract
Herein, we describe the application of a flow system for the generation of a soluble organo sodium compound and the transformation of this primary nucleophile with various Weinreb amides for the synthesis of alkyl-aryl ketones. Thereafter, the generation of secondary sodium intermediates, such as benzylic sodium nucleophiles or ortho-metalated sodium nucleophiles from various carbon pre-nucleophiles, is described. These transformations generated more complex ketones, and in this investigation the key aspect was to identify factors for the chemoselective and regioselective C-H deprotonation of concurring sites within the starting material. Finally, the direct synthesis of ketones from carboxylic acids and the organo sodium compound is described, revealing interesting aspects regarding the nucleophilicity and basicity of the alkyl sodium reagent.
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Affiliation(s)
- Paula Knupe-Wolfgang
- Institute of Chemistry, Carl von Ossietzky University Oldenburg, Carl-von-Ossietzky-Straße 9-11, 26129 Oldenburg, Germany
| | - Bennett Mahn
- Institute of Chemistry, Carl von Ossietzky University Oldenburg, Carl-von-Ossietzky-Straße 9-11, 26129 Oldenburg, Germany
| | - Gerhard Hilt
- Institute of Chemistry, Carl von Ossietzky University Oldenburg, Carl-von-Ossietzky-Straße 9-11, 26129 Oldenburg, Germany
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2
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Duari P, Mondal S, Jörges M, Gessner VH. The lithium effect in ketenyl anion chemistry. Chem Commun (Camb) 2024. [PMID: 39139106 PMCID: PMC11322804 DOI: 10.1039/d4cc03167a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2024] [Accepted: 08/01/2024] [Indexed: 08/15/2024]
Abstract
Ketenyl lithium compounds of type [RC(Li)CO] (with R = Ph2P(E), E = O, S, Se) were found to exhibit lower thermal stabilities than their potassium analogues due to the stronger coordination of the oxygen of the ketene moiety to the harder metal cation, resulting in a more pronounced ynolate character. Using additional ligands allows manipulation of the O-Li interaction, thereby influencing the stability and reactivity of the ketenyl anions.
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Affiliation(s)
- Prakash Duari
- Faculty of Chemistry and Biochemistry, Ruhr-University Bochum, 44801 Bochum, Germany.
| | - Sunita Mondal
- Faculty of Chemistry and Biochemistry, Ruhr-University Bochum, 44801 Bochum, Germany.
| | - Mike Jörges
- Faculty of Chemistry and Biochemistry, Ruhr-University Bochum, 44801 Bochum, Germany.
| | - Viktoria H Gessner
- Faculty of Chemistry and Biochemistry, Ruhr-University Bochum, 44801 Bochum, Germany.
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3
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Spivey JA, Collum DB. Potassium Hexamethyldisilazide (KHMDS): Solvent-Dependent Solution Structures. J Am Chem Soc 2024; 146:17827-17837. [PMID: 38901126 DOI: 10.1021/jacs.4c03418] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/22/2024]
Abstract
Solution structures of potassium hexamethyldisilazide [KHMDS] and labeled [15N]KHMDS were examined using a number of analytical methods including 29Si NMR spectroscopy and density functional theory computations. A combination of 15N-29Si couplings, 29Si chemical shifts, and the method of continuous variations reveals dimers, monomers, and ion pairs. Weakly coordinating monofunctional ligands such as toluene, N,N-dimethylethylamine, and Et3N afford exclusively dimers. 1,3-Dioxolane, THF, dimethoxyethane, hexamethylphosphoramide, and diglyme provide dimers at low ligand concentrations and monomers at high ligand concentrations. N,N,N',N'-Tetramethylethylenediamine and N,N,N',N'-tetramethylcyclohexanediamine provide exclusively dimers at all ligand concentrations at ambient temperatures and significant monomer at -80 °C. Studies of 12-crown-4 ran into technical problems. Equimolar 15-crown-5 forms a dimer, whereas excess 15-crown-5 affords a putative ion pair. Whereas equimolar 18-crown-6 also affords a dimer, an excess provides a monomer rather than a solvent-separated ion pair. [2.2.2]cryptand affords what is believed to be a contact-ion-paired cryptate. Solvation was probed using largely density functional theory (DFT) computations. Thermally corrected energies are consistent with lower aggregates and higher solvates at low temperatures, but the magnitudes of the computed temperature dependencies were substantially larger than the experimentally derived data.
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Affiliation(s)
- Jesse A Spivey
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, United States
| | - David B Collum
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, United States
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4
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Sreedharan R, Gandhi T. Masters of Mediation: MN(SiMe 3) 2 in Functionalization of C(sp 3)-H Latent Nucleophiles. Chemistry 2024; 30:e202400435. [PMID: 38497321 DOI: 10.1002/chem.202400435] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Revised: 03/16/2024] [Accepted: 03/18/2024] [Indexed: 03/19/2024]
Abstract
Organoalkali compounds have undergone a far-reaching transformation being a coupling partner to a mediator in unusual organic conversions which finds its spot in the field of sustainable synthesis. Transition-metal catalysis has always been the priority in C(sp3)-H bond functionalization, however alternatively, in recent times this has been seriously challenged by earth-abundant alkali metals and their complexes arriving at new sustainable organometallic reagents. In this line, the importance of MN(SiMe3)2 (M=Li, Na, K & Cs) reagent revived in C(sp3)-H bond functionalization over recent years in organic synthesis is showcased in this minireview. MN(SiMe3)2 reagent with higher reactivity, enhanced stability, and bespoke cation-π interaction have shown eye-opening mediated processes such as C(sp3)-C(sp3) cross-coupling, radical-radical cross-coupling, aminobenzylation, annulation, aroylation, and other transformations to utilize readily available petrochemical feedstocks. This article also emphasizes the unusual reactivity of MN(SiMe3)2 reagent in unreactive and robust C-X (X=O, N, F, C) bond cleavage reactions that occurred alongside the C(sp3)-H bond functionalization. Overall, this review encourages the community to exploit the untapped potential of MN(SiMe3)2 reagent and also inspires them to take up this subject to even greater heights.
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Affiliation(s)
- Ramdas Sreedharan
- Department of Chemistry, School of Advanced Sciences, Vellore Institute of Technology, Vellore, 632014, Tamil Nadu, India
| | - Thirumanavelan Gandhi
- Department of Chemistry, School of Advanced Sciences, Vellore Institute of Technology, Vellore, 632014, Tamil Nadu, India
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5
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Macdonald PA, Kennedy AR, Weetman CE, Robertson SD, Mulvey RE. Synthesis, characterisation, and catalytic application of a soluble molecular carrier of sodium hydride activated by a substituted 4-(dimethylamino)pyridine. Commun Chem 2024; 7:94. [PMID: 38678145 PMCID: PMC11055874 DOI: 10.1038/s42004-024-01184-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2024] [Accepted: 04/18/2024] [Indexed: 04/29/2024] Open
Abstract
Recently main group compounds have stepped into the territory of precious transition metal compounds with respect to utility in the homogeneous catalysis of fundamentally important organic transformations. Inspired by the need to promote more sustainability in chemistry because of their greater abundance in nature, this change of direction is surprising since main group metals generally do not possess the same breadth of reactivity as precious transition metals. Here, we introduce the dihydropyridylsodium compound, Na-1,2-tBu-DH(DMAP), and its monomeric variant [Na-1,2-tBu-DH(DMAP)]·Me6TREN, and demonstrate their effectiveness in transfer hydrogenation catalysis of the representative alkene 1,1-diphenylethylene to the alkane 1,1-diphenylethane using 1,4-cyclohexadiene as hydrogen source [DMAP = 4-dimethylaminopyridine; Me6TREN = tris(N,N-dimethyl-2-aminoethyl)amine]. Sodium is appealing because of its high abundance in the earth's crust and oceans, but organosodium compounds have been rarely used in homogeneous catalysis. The success of the dihydropyridylsodium compounds can be attributed to their high solubility and reactivity in organic solvents.
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Affiliation(s)
- Peter A Macdonald
- WestCHEM, Department of Pure & Applied Chemistry, University of Strathclyde, Glasgow, G1 1XL, UK
| | - Alan R Kennedy
- WestCHEM, Department of Pure & Applied Chemistry, University of Strathclyde, Glasgow, G1 1XL, UK
| | - Catherine E Weetman
- WestCHEM, Department of Pure & Applied Chemistry, University of Strathclyde, Glasgow, G1 1XL, UK
| | - Stuart D Robertson
- WestCHEM, Department of Pure & Applied Chemistry, University of Strathclyde, Glasgow, G1 1XL, UK.
| | - Robert E Mulvey
- WestCHEM, Department of Pure & Applied Chemistry, University of Strathclyde, Glasgow, G1 1XL, UK.
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6
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Davison N, Hemingway JM, Waddell PG, Lu E. Lithium, sodium and potassium enolate aggregates and monomers: syntheses and structures. Dalton Trans 2024; 53:4719-4728. [PMID: 38362928 DOI: 10.1039/d4dt00211c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2024]
Abstract
In this Article, we report the syntheses and comparative structural studies of lithium, sodium, and potassium anthracen-9-yl enolates, as their aggregates (Li, Na: hexamer; K: tetramer) and ligand-stabilized monomers (for Li and Na). The monomers add new members to the rare collection of group-1 metal monomeric enolates. Moreover, the series covers different group-1 metal cations (Li+, Na+ and K+) and aggregate sizes, allowing comparative structural studies to elucidate how the metal identity and aggregate size influence the enolate structure.
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Affiliation(s)
- Nathan Davison
- Chemistry-School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK.
| | - Jack M Hemingway
- Chemistry-School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK.
| | - Paul G Waddell
- Chemistry-School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK.
| | - Erli Lu
- Chemistry-School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK.
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7
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Anderson DE, Tortajada A, Hevia E. New Frontiers in Organosodium Chemistry as Sustainable Alternatives to Organolithium Reagents. Angew Chem Int Ed Engl 2024; 63:e202313556. [PMID: 37801443 DOI: 10.1002/anie.202313556] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Revised: 10/05/2023] [Accepted: 10/06/2023] [Indexed: 10/08/2023]
Abstract
With their highly reactive respective C-Na and N-Na bonds, organosodium and sodium amide reagents could be viewed as obvious replacements or even superior reagents to the popular, widely utilised organolithiums. However, they have seen very limited applications in synthesis due mainly to poor solubility in common solvents and their limited stability. That notwithstanding in recent years there has been a surge of interest in bringing these sustainable metal reagents into the forefront of organometallics in synthesis. Showcasing the growth in utilisation of organosodium complexes within several areas of synthetic chemistry, this Minireview discusses promising new methods that have been recently reported with the goal of taming these powerful reagents. Special emphasis is placed on coordination and aggregation effects in these reagents which can impart profound changes in their solubility and reactivity. Differences in observed reactivity between more nucleophilic aryl and alkyl sodium reagents and the less nucleophilic but highly basic sodium amides are discussed along with current mechanistic understanding of their reactivities. Overall, this review aims to inspire growth in this exciting field of research to allow for the integration of organosodium complexes within common important synthetic transformations.
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Affiliation(s)
- David E Anderson
- Department für Chemie und Biochemie, Universität Bern, Freiestrasse 3, 3012, Bern, Switzerland
| | - Andreu Tortajada
- Department für Chemie und Biochemie, Universität Bern, Freiestrasse 3, 3012, Bern, Switzerland
| | - Eva Hevia
- Department für Chemie und Biochemie, Universität Bern, Freiestrasse 3, 3012, Bern, Switzerland
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8
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You Q, Collum DB. Carbon-Nitrogen Bond Formation Using Sodium Hexamethyldisilazide: Solvent-Dependent Reactivities and Mechanisms. J Am Chem Soc 2023; 145:23568-23584. [PMID: 37857357 DOI: 10.1021/jacs.3c07317] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2023]
Abstract
The solvent-dependent reactivity of sodium hexamethyldisilazide (NaHMDS) toward carbon-centered electrophiles reveals reactions that are poorly represented or unrepresented in the literature, including direct aminolysis of aromatic methyl esters to give carboxamides, nitriles, or amidines, depending on the choice of solvent. SNAr substitutions of aryl halides and opening of terminal epoxides are also examined. A combination of 1H and 29Si nuclear magnetic resonance (NMR) spectroscopic studies using [15N]NaHMDS, kinetic studies, and computational studies reveals the complex mechanistic basis of the preferences for simple aryl carboxamides in toluene and dimethylethylamine and arylnitriles or amidines in tetrahydrofuran (THF). A prevalence of dimer- and mixed dimer-based chemistry even starting from the observable NaHMDS monomer in THF solution is notable.
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Affiliation(s)
- Qiulin You
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, United States
| | - David B Collum
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, United States
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9
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Malik M, Senatore R, Langer T, Holzer W, Pace V. Base-mediated homologative rearrangement of nitrogen-oxygen bonds of N-methyl- N-oxyamides. Chem Sci 2023; 14:10140-10146. [PMID: 37772102 PMCID: PMC10530184 DOI: 10.1039/d3sc03216g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2023] [Accepted: 08/26/2023] [Indexed: 09/30/2023] Open
Abstract
Due to the well known reactivity of C(O)-N functionalities towards canonical C1-homologating agents (e.g. carbenoids, diazomethane, ylides), resulting in the extrusion of the N-centered fragment en route to carbonyl compounds, formal C1-insertions within N-O bonds still remain obscure. Herein, we document the homologative transformation of N-methyl-N-oxyamides - with high tolerance for diverse O-substituents - into N-acyl-N,O-acetals. Under controlled basic conditions, the N-methyl group of the same starting materials acts as a competent precursor of the methylene synthon required for the homologation. The logic is levered on the formation of an electrophilic iminium ion (via N-O heterolysis) susceptible to nucleophilic attack by the alkoxide previously expulsed. The procedure documents genuine chemocontrol and flexibility, as judged by the diversity of substituents placed on both amide and nitrogen linchpins. The mechanistic rationale was validated through experiments conducted on D-labeled materials which unambiguously attributed the origin of the methylene fragment to the N-methyl group of the starting compounds.
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Affiliation(s)
- Monika Malik
- Department of Pharmaceutical Sciences, Division of Pharmaceutical Chemistry, University of Vienna Josef-Holaubek-Platz 2 1090 Vienna Austria
| | - Raffaele Senatore
- Department of Pharmaceutical Sciences, Division of Pharmaceutical Chemistry, University of Vienna Josef-Holaubek-Platz 2 1090 Vienna Austria
| | - Thierry Langer
- Department of Pharmaceutical Sciences, Division of Pharmaceutical Chemistry, University of Vienna Josef-Holaubek-Platz 2 1090 Vienna Austria
| | - Wolfgang Holzer
- Department of Pharmaceutical Sciences, Division of Pharmaceutical Chemistry, University of Vienna Josef-Holaubek-Platz 2 1090 Vienna Austria
| | - Vittorio Pace
- Department of Pharmaceutical Sciences, Division of Pharmaceutical Chemistry, University of Vienna Josef-Holaubek-Platz 2 1090 Vienna Austria
- Department of Chemistry, University of Turin Via Giuria 7 10125 Turin Italy
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10
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Tortajada A, Bole LJ, Mu M, Stanford M, Peñas-Defrutos MN, García-Melchor M, Hevia E. Sodium mediated deprotonative borylation of arenes using sterically demanding B(CH 2SiMe 3) 3: unlocking polybasic behaviour and competing lateral borane sodiation. Chem Sci 2023; 14:6538-6545. [PMID: 37350840 PMCID: PMC10283504 DOI: 10.1039/d3sc01705b] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Accepted: 05/04/2023] [Indexed: 06/24/2023] Open
Abstract
The deprotonative metalation of organic molecules has become a convenient route to prepare functionalised aromatic substrates. Amongst the different metallating reagents available, sodium bases have recently emerged as a more sustainable and powerful alternative to their lithium analogues. Here we report the study of the sterically demanding electrophilic trap B(CH2SiMe3)3 for the deprotonative borylation of arenes using NaTMP (TMP = 2,2,6,6-tetramethylpiperidide) in combination with tridentate Lewis donor PMDETA (PMDETA = N,N,N',N'',N''-pentamethyldiethylenetriamine). Using anisole and benzene as model substrates, unexpected polybasic behaviour has been uncovered, which enables the formal borylation of two equivalents of the relevant arene. The combination of X-ray crystallographic and NMR monitoring studies with DFT calculations has revealed that while the first B-C bond forming process takes place via a sodiation/borylation sequence to furnish [(PMDETA)NaB(Ar)(CH2SiMe3)3] species, the second borylation step is facilitated by the formation of a borata-alkene intermediate, without the need of an external base. For non-activated benzene, it has also been found that under stoichimetric conditions the lateral sodiation of B(CH2SiMe3)3 becomes a competitive reaction pathway furnishing a novel borata-alkene complex. Showing a clear alkali-metal effect, the use of the sodium base is key to access this reactivity, while the metalation/borylation of the amine donor PMDETA is observed instead when LiTMP is used.
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Affiliation(s)
- Andreu Tortajada
- Department für Chemie und Biochemie, Universität Bern Freiestrasse 3 3012 Bern Switzerland
| | - Leonie J Bole
- Department für Chemie und Biochemie, Universität Bern Freiestrasse 3 3012 Bern Switzerland
| | - Manting Mu
- School of Chemistry, CRANN and AMBER Research Centres, Trinity College Dublin College Green Dublin 2 Ireland
| | - Martin Stanford
- Department für Chemie und Biochemie, Universität Bern Freiestrasse 3 3012 Bern Switzerland
| | - Marconi N Peñas-Defrutos
- School of Chemistry, CRANN and AMBER Research Centres, Trinity College Dublin College Green Dublin 2 Ireland
- IU CINQUIMA/Química Inorgánica, Facultad de Ciencias, Universidad de Valladolid 47071-Valladolid Spain
| | - Max García-Melchor
- School of Chemistry, CRANN and AMBER Research Centres, Trinity College Dublin College Green Dublin 2 Ireland
| | - Eva Hevia
- Department für Chemie und Biochemie, Universität Bern Freiestrasse 3 3012 Bern Switzerland
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11
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Borys AM, Hevia E. Organolithium aggregation as a blueprint to construct polynuclear lithium nickelate clusters. Chem Commun (Camb) 2023. [PMID: 37191064 DOI: 10.1039/d3cc01729j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
By exploiting the high aggregation of aliphatic lithium acetylides, here we report the synthesis and structural analysis of polynuclear lithium nickelate clusters in which up to 10 equivalents of organolithium can co-complex per Ni(0) centre. Exposure of the Ni(0)-ate clusters to dry air provides an alternative route to homoleptic Ni(II)-ates.
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Affiliation(s)
- Andryj M Borys
- Departement für Chemie, Biochemie und Pharmazie, Universität Bern, Bern 3012, Switzerland.
| | - Eva Hevia
- Departement für Chemie, Biochemie und Pharmazie, Universität Bern, Bern 3012, Switzerland.
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12
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Davison N, McMullin CL, Zhang L, Hu SX, Waddell PG, Wills C, Dixon C, Lu E. Li vs Na: Divergent Reaction Patterns between Organolithium and Organosodium Complexes and Ligand-Catalyzed Ketone/Aldehyde Methylenation. J Am Chem Soc 2023; 145:6562-6576. [PMID: 36890641 PMCID: PMC10037334 DOI: 10.1021/jacs.3c01033] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/10/2023]
Abstract
Organosodium chemistry is underdeveloped compared with organolithium chemistry, and all the reported organosodium complexes exhibit similar, if not identical, reactivity patterns to their lithium counterparts. Herein, we report a rare organosodium monomeric complex, namely, [Na(CH2SiMe3)(Me6Tren)] (1-Na) (Me6Tren: tris[2-(dimethylamino)ethyl]amine) stabilized by a tetra-dentate neutral amine ligand Me6Tren. Employing organo-carbonyl substrates (ketones, aldehydes, amides, ester), we demonstrated that 1-Na features distinct reactivity patterns compared with its lithium counterpart, [Li(CH2SiMe3)(Me6Tren)] (1-Li). Based on this knowledge, we further developed a ligand-catalysis strategy to conduct ketone/aldehyde methylenations, using [NaCH2SiMe3]∞ as the CH2 feedstock, replacing the widely used but hazardous/expensive C═O methylenation methods, such as Wittig, Tebbe, Julia/Julia-Kocieński, Peterson, and so on.
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Affiliation(s)
- Nathan Davison
- Chemistry-School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne NE1 7RU, U.K
| | - Claire L McMullin
- Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, U.K
| | - Lu Zhang
- School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083, P. R. China
| | - Shu-Xian Hu
- School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083, P. R. China
| | - Paul G Waddell
- Chemistry-School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne NE1 7RU, U.K
| | - Corinne Wills
- Chemistry-School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne NE1 7RU, U.K
| | - Casey Dixon
- Chemistry-School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne NE1 7RU, U.K
| | - Erli Lu
- Chemistry-School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne NE1 7RU, U.K
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