1
|
Akama H, Kojima KM, McKenzie I, Ito S. Producing Conventional and Transient Amino(mercapto)methyl Radicals by Addition of Muonium to a Crystalline Thioformamide (Mes*NHCH=S). Chemphyschem 2024; 25:e202300980. [PMID: 38515308 DOI: 10.1002/cphc.202300980] [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: 12/21/2023] [Revised: 03/21/2024] [Accepted: 03/21/2024] [Indexed: 03/23/2024]
Abstract
Muonium (Mu=μ+e-) is composed of a muon of light isotope of proton (μ+) and electron (e-) and can be used as a light surrogate for a hydrogen atom. In this paper, we investigated addition of muonium to a newly synthesized Mes*-substituted thioformamide (Mes*NHCH=S, Mes*=2,4,6-tBu3C6H2). Transverse-field muon spin rotation (TF-μSR) of a solution sample of the thioformamide confirmed addition of muonium to the sulfur atom leading to the corresponding C-centered radical [Mes*NHC(H)⋅-SMu]. Density functional theory (DFT) calculations assigned a conventional amino(mercapto)methyl radical, in which both nitrogen and carbon were slightly pyramidalized, and the calculated muon hyperfine coupling constant (hfcc) including the muon isotope effect was compatible with the experimentally determined parameter. However, the muon level-crossing resonance (μLCR) spectrum of an anisotropic crystalline sample indicated two paramagnetic species, and the major product showed the considerably larger muon hfcc compared with the conventional structure of the amino(mercapto)methyl radical. The unusual transient muoniated thioformamide with the larger muon hfcc that showed rapid relaxation could be only explained by a transient structure including planarization of the nitrogen and carbon atoms in Mes*NHC(H)⋅-SMu.
Collapse
Affiliation(s)
- Hikaru Akama
- Department of Applied Chemistry, School of Materials and Chemical Technology, Tokyo Institute of Technology, 2-12-1-H113 Ookayama, Meguro-ku, Tokyo, 152-8552, Japan
| | - Kenji M Kojima
- Centre for Molecular and Materials Science, TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3, Canada
| | - Iain McKenzie
- Centre for Molecular and Materials Science, TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3, Canada
| | - Shigekazu Ito
- Department of Applied Chemistry, School of Materials and Chemical Technology, Tokyo Institute of Technology, 2-12-1-H113 Ookayama, Meguro-ku, Tokyo, 152-8552, Japan
| |
Collapse
|
2
|
Walsgrove HTG, Percival PW, Gates DP. Probing Radical Addition to 1-Phosphabutadienes by Employing Muonium as a "Light Isotope" of Hydrogen. Chemistry 2024; 30:e202302869. [PMID: 37837229 DOI: 10.1002/chem.202302869] [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: 09/03/2023] [Revised: 10/08/2023] [Accepted: 10/11/2023] [Indexed: 10/15/2023]
Abstract
Understanding free radical addition to multiple bonds is important to elucidating the mechanistic details of addition polymerization reactions, albeit the fleeting radical intermediates are very difficult to detect by conventional methodologies. Muon spin spectroscopy (μSR) is a highly sensitive method that can detect radical species at 106 spins (cf. EPR: 1012 spins, NMR: 1018 spins). Herein, we employ μSR to detect the radical-addition products from three 1-phosphabutadiene monomers, P-analogues of isoprene. We show that muonium (Mu), a "light" H-atom surrogate, adds predominantly at the C4 position of the P1 =C2 -C3 =C4 moiety to give unprecedented 1-phosphaallyl radicals as the major products. Our structural assignments are supported by assignment of muon, phosphorus and proton hyperfine coupling constants using DFT-calculations. A minor radical product is also detected that is tentatively assigned to an PC3 -heterocyclic free radical. On the basis of DFT-predictions, we speculate that its formation may involve initial addition of Mu+ at the C3 position followed by electron capture. These studies provide rare insights into the prospective radical (or cationic) polymerization of 1-phosphabutadienes, which have previously been polymerized using anionic initiation.
Collapse
Affiliation(s)
- Henry T G Walsgrove
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia, V6T 1Z1, Canada
| | - Paul W Percival
- Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, V5A 1S6, Canada
- Centre for Molecular and Materials Science TRIUMF, Vancouver, British Columbia, V6T 2A3, Canada
| | - Derek P Gates
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia, V6T 1Z1, Canada
| |
Collapse
|
3
|
Percival PW, Brodovitch JC. The Reaction of Muonium with Hydrogen Peroxide in Aqueous Solution. Chemphyschem 2023; 24:e202300288. [PMID: 37614034 DOI: 10.1002/cphc.202300288] [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: 04/23/2023] [Revised: 08/22/2023] [Accepted: 08/23/2023] [Indexed: 08/25/2023]
Abstract
Rate constants for the reactions of muonium (Mu) (the ultralight isotope of the hydrogen atom) with H2 O2 in H2 O and D2 O2 in D2 O have been determined at various temperatures and pH (pD) values. The data are consistent with the three reactions:Mu + H 2 O 2 → k 1 M products ${{\rm{Mu}} + {\rm{H}}_2 {\rm{O}}_2 \mathop \rightarrow \limits ^{{k_{1{\rm{M}}} }}_{} {\rm{products}}}$ ,Mu + HO 2 - → k 2 M products ${{\rm{Mu}} + {\rm{HO}}_2^ - \mathop \rightarrow \limits ^{{k_{2{\rm{M}}} }}_{} {\rm{products}}}$ ,Mu + O - → k 3 M products ${{\rm{Mu}} + {\rm{O}}^ - \mathop \rightarrow \limits ^{{k_{3{\rm{M}}} }}_{} {\rm{products}}}$ and the equivalent for the deuterated entities. A significant positive H/D isotope effect was found for the undissociated peroxide, while for the anions the effect was negligible or slightly in the opposite direction. In addition, for concentrated solutions of peroxide a study of the muon spin polarization as a function of applied transverse magnetic field yielded results consistent with the rate constants determined from the direct decay measurements, and indicated that the reaction products are diamagnetic, most likely MuH and MuOH, i. e., no muoniated radical products are formed. These results are potentially relevant for management of the radiolysis products in nuclear industry.
Collapse
Affiliation(s)
- Paul W Percival
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada
- Centre for Molecular and Materials Science, TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3, Canada
| | - Jean-Claude Brodovitch
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada
| |
Collapse
|
4
|
Ito S. Muon Spin Rotation/Resonance (μSR) for Studying Radical Reactivity of Unsaturated Organophosphorus Compounds. Chemistry 2022; 28:e202200843. [PMID: 35702738 PMCID: PMC9796767 DOI: 10.1002/chem.202200843] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Indexed: 01/07/2023]
Abstract
The positive muon (μ+ ) can be regarded as a light isotope of proton and has been an important tool to study radical reactions of organic compounds. Recently, muons have been applied to produce short-lived paramagnetic species from the heavier unsaturated organic molecules including the p-block elements. This article overviews recent muon spin rotation/resonance (μSR) studies on the phosphorus analogs of alkenes, anthracenes, and cyclobutane-1,3-diyls together with the fundamentals of μSR. The acyclic phosphaalkene of P=C and phosphasilenes of P=Si can accept muonium (Mu=[μ+ e- ]) at the heavier double bonds, and the corresponding radicals have been characterized. The phosphorus atom in 9-phosphaanthracene, whose P=C double bond is stabilized by the peri-substituted CF3 groups, predominantly captures muonium to provide the corresponding paramagnetic fused heterocyclic system. The peri-trifluoromethyl groups are functional to promote the unprecedented light isotope effect of muon providing the planar three-cyclic molecular structure to consume the increased zero-point energy. The formally open-shell singlet 1,3-diphosphacyclobutane-2,4-diyl unit can accept muonium at the (ylidic) phosphorus or the skeletal radicalic carbon, and the corresponding paramagnetic phosphorus heterocycles can be characterized by μSR. The findings on these muoniation processes to the unsaturated phosphorus-containing compounds will contribute not only to development of novel paramagnetic functional species but also to progress on muon science.
Collapse
Affiliation(s)
- Shigekazu Ito
- Department of Applied ChemistrySchool of Materials and Chemical TechnologyTokyo Institute of Technology2-12-1-H113 Ookayama, Meguro-kuTokyo152-8552Japan
| |
Collapse
|
5
|
McFadden RML, Szunyogh D, Bravo‐Frank N, Chatzichristos A, Dehn MH, Fujimoto D, Jancsó A, Johannsen S, Kálomista I, Karner VL, Kiefl RF, Larsen FH, Lassen J, Levy CDP, Li R, McKenzie I, McPhee H, Morris GD, Pearson MR, Sauer SPA, Sigel RKO, Thulstrup PW, MacFarlane WA, Hemmingsen L, Stachura M. Magnesium(II)‐ATP Complexes in 1‐Ethyl‐3‐Methylimidazolium Acetate Solutions Characterized by
31
Mg β‐Radiation‐Detected NMR Spectroscopy. Angew Chem Int Ed Engl 2022; 61:e202207137. [PMID: 35718746 PMCID: PMC9539566 DOI: 10.1002/anie.202207137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Indexed: 11/26/2022]
Abstract
The complexation of MgII with adenosine 5′‐triphosphate (ATP) is omnipresent in biochemical energy conversion, but is difficult to interrogate directly. Here we use the spin‐1/2
β‐emitter 31Mg to study MgII‐ATP complexation in 1‐ethyl‐3‐methylimidazolium acetate (EMIM‐Ac) solutions using β‐radiation‐detected nuclear magnetic resonance (β‐NMR). We demonstrate that (nuclear) spin‐polarized 31Mg, following ion‐implantation from an accelerator beamline into EMIM‐Ac, binds to ATP within its radioactive lifetime before depolarizing. The evolution of the spectra with solute concentration indicates that the implanted 31Mg initially bind to the solvent acetate anions, whereafter they undergo dynamic exchange and form either a mono‐ (31Mg‐ATP) or di‐nuclear (31MgMg‐ATP) complex. The chemical shift of 31Mg‐ATP is observed up‐field of 31MgMg‐ATP, in accord with quantum chemical calculations. These observations constitute a crucial advance towards using β‐NMR to probe chemistry and biochemistry in solution.
Collapse
Affiliation(s)
| | - Dániel Szunyogh
- Department of Chemistry University of Copenhagen Universitetsparken 5 2100 Copenhagen Denmark
| | - Nicholas Bravo‐Frank
- Faculty of Engineering University of Victoria 3800 Finnerty Road Victoria BC V8P 5C2 Canada
| | - Aris Chatzichristos
- Department of Physics and Astronomy University of British Columbia 6224 Agricultural Road Vancouver BC V6T 1Z1 Canada
- Stewart Blusson Quantum Matter Institute University of British Columbia 2355 East Mall Vancouver BC V6T 1Z4 Canada
| | - Martin H. Dehn
- Department of Physics and Astronomy University of British Columbia 6224 Agricultural Road Vancouver BC V6T 1Z1 Canada
- Stewart Blusson Quantum Matter Institute University of British Columbia 2355 East Mall Vancouver BC V6T 1Z4 Canada
| | - Derek Fujimoto
- Department of Physics and Astronomy University of British Columbia 6224 Agricultural Road Vancouver BC V6T 1Z1 Canada
- Stewart Blusson Quantum Matter Institute University of British Columbia 2355 East Mall Vancouver BC V6T 1Z4 Canada
| | - Attila Jancsó
- Department of Inorganic and Analytical Chemistry University of Szeged Dóm tér 7 6720 Szeged Hungary
| | - Silke Johannsen
- Department of Chemistry University of Zurich Winterthurerstrasse 190 8057 Zürich Switzerland
| | - Ildikó Kálomista
- Department of Chemistry University of Copenhagen Universitetsparken 5 2100 Copenhagen Denmark
| | - Victoria L. Karner
- Stewart Blusson Quantum Matter Institute University of British Columbia 2355 East Mall Vancouver BC V6T 1Z4 Canada
- Department of Chemistry University of British Columbia 2036 Main Mall Vancouver BC V6T 1Z1 Canada
| | - Robert F. Kiefl
- TRIUMF 4004 Wesbrook Mall Vancouver BC V6T 2A3 Canada
- Department of Physics and Astronomy University of British Columbia 6224 Agricultural Road Vancouver BC V6T 1Z1 Canada
- Stewart Blusson Quantum Matter Institute University of British Columbia 2355 East Mall Vancouver BC V6T 1Z4 Canada
| | - Flemming H. Larsen
- Department of Food Science University of Copenhagen Rolighedsvej 26 1958 Frederiksberg Denmark
| | - Jens Lassen
- TRIUMF 4004 Wesbrook Mall Vancouver BC V6T 2A3 Canada
- Department of Physics Simon Fraser University 8888 University Drive Burnaby BC V5A 1S6 Canada
- Department of Physics and Astronomy University of Manitoba 30A Sifton Road Winnipeg MB R3T 2N2 Canada
| | | | - Ruohong Li
- TRIUMF 4004 Wesbrook Mall Vancouver BC V6T 2A3 Canada
| | - Iain McKenzie
- TRIUMF 4004 Wesbrook Mall Vancouver BC V6T 2A3 Canada
- Department of Chemistry Simon Fraser University 8888 University Drive Burnaby BC V5A 1S6 Canada
- Department of Physics and Astronomy University of Waterloo 200 University Avenue West Waterloo ON N2L 3G1 Canada
| | - Hannah McPhee
- Department of Engineering McMaster University 1280 Main Street West Hamilton ON L8S 4L7 Canada
| | | | | | - Stephan P. A. Sauer
- Department of Chemistry University of Copenhagen Universitetsparken 5 2100 Copenhagen Denmark
| | - Roland K. O. Sigel
- Department of Chemistry University of Zurich Winterthurerstrasse 190 8057 Zürich Switzerland
| | - Peter W. Thulstrup
- Department of Chemistry University of Copenhagen Universitetsparken 5 2100 Copenhagen Denmark
| | - W. Andrew MacFarlane
- TRIUMF 4004 Wesbrook Mall Vancouver BC V6T 2A3 Canada
- Department of Physics and Astronomy University of British Columbia 6224 Agricultural Road Vancouver BC V6T 1Z1 Canada
- Department of Chemistry University of British Columbia 2036 Main Mall Vancouver BC V6T 1Z1 Canada
| | - Lars Hemmingsen
- Department of Chemistry University of Copenhagen Universitetsparken 5 2100 Copenhagen Denmark
| | - Monika Stachura
- TRIUMF 4004 Wesbrook Mall Vancouver BC V6T 2A3 Canada
- Department of Chemistry Simon Fraser University 8888 University Drive Burnaby BC V5A 1S6 Canada
| |
Collapse
|
6
|
McKenzie I, Cannon J, Cordoni-Jordan D, Mulley BP, Scheuermann R. Paramagnetic probes in an organic semiconductor: μSR and DFT calculations of the Mu adducts of Alq 3 and 8-hydroxyquinoline. J Chem Phys 2022; 157:064702. [PMID: 35963724 DOI: 10.1063/5.0105200] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
It has been claimed that longitudinal field muon spin relaxation (LF-μSR) experiments on the organic semiconductor (OSC) tris-(8-hydroxyquinoline)aluminum(III) (Alq3) have measured electron hopping rates of ∼1012s-1, while density functional theory (DFT) calculations suggest that electron hopping between a muoniated radical and a neighboring molecule is energetically unfavorable and that the LF-μSR experiments were probing muoniated radicals with localized spin density. We have performed avoided level crossing muon spin resonance (ALC-μSR) and transverse field muon spin rotation (TF-μSR) measurements on Alq3 and 8-hydroxyquinoline (8hq), which is meant to model the muoniated radicals present in Alq3 when they are not in an OSC. These are supplemented by benchmarked DFT calculations. The ALC-μSR and TF-μSR spectra of 8hq and Alq3 are best explained by Mu adding to all six secondary carbons of the quinolate rings with roughly equal yields and localized spin density. There is no evidence in the TF-μSR spectrum of Alq3 for the formation of radicals with muon hyperfine coupling constants of 23 or 91 MHz as reported earlier by others. Our measurements support the view that there is localized spin density on the molecule to which Mu is covalently bound and the muon is not a passive probe in organic systems as it can be incorporated into radicals that have different electronic structures to the parent compounds. The muoniated radicals in Alq3 are more short-lived than in 8hq, which could be due to interactions with mobile electrons in the OSC, but with electron spin flip rates on the order of ∼107s-1.
Collapse
Affiliation(s)
- Iain McKenzie
- Centre for Molecular and Materials Science, TRIUMF, Vancouver, British Columbia V6T 2A3, Canada
| | - Joseph Cannon
- School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA, United Kingdom
| | - Danaan Cordoni-Jordan
- Department of Chemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
| | - Brian P Mulley
- Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Robert Scheuermann
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, Villigen AG 5232, Switzerland
| |
Collapse
|
7
|
McFadden RML, Szunyogh D, Bravo-Frank N, Chatzichristos A, Dehn MH, Fujimoto D, Jancsó A, Johannsen S, Kálomista I, Karner VL, Kiefl RF, Larsen FH, Lassen J, Levy CDP, Li R, McKenzie I, McPhee H, Morris GD, Pearson MR, Sauer SPA, Sigel RKO, Thulstrup PW, MacFarlane WA, Hemmingsen L, Stachura M. Magnesium(II)‐ATP Complexes in 1‐Ethyl‐3‐Methylimidazolium Acetate Solutions Characterized by 31Mg β‐Radiation‐Detected NMR Spectroscopy. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202207137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
| | - Dániel Szunyogh
- University of Copenhagen: Kobenhavns Universitet Department of Chemistry DENMARK
| | - Nicholas Bravo-Frank
- University of Victoria Faculty of Engineering: University of Victoria Faculty of Engineering & Computer Science Faculty of Engineering CANADA
| | - Aris Chatzichristos
- The University of British Columbia Department of Physics and Astronomy CANADA
| | - Martin H. Dehn
- The University of British Columbia Department of Physics and Astronomy CANADA
| | - Derek Fujimoto
- The University of British Columbia Department of Physics and Astronomy CANADA
| | - Attila Jancsó
- University of Szeged: Szegedi Tudomanyegyetem Department of Inorganic and Analytical Chemistry HUNGARY
| | - Silke Johannsen
- University of Zurich: Universitat Zurich Department of Chemistry SWITZERLAND
| | - Ildikó Kálomista
- University of Copenhagen: Kobenhavns Universitet Department of Chemistry DENMARK
| | | | - Robert F. Kiefl
- The University of British Columbia Department of Physics and Astronomy CANADA
| | - Flemming H. Larsen
- University of Copenhagen: Kobenhavns Universitet Department of Food Science DENMARK
| | | | | | | | | | - Hannah McPhee
- McMaster University Department of Engineering Physics CANADA
| | | | | | - Stephan P. A. Sauer
- University of Copenhagen: Kobenhavns Universitet Department of Chemistry DENMARK
| | - Roland K. O. Sigel
- University of Zurich: Universitat Zurich Department of Chemistry SWITZERLAND
| | - Peter W. Thulstrup
- University of Copenhagen: Kobenhavns Universitet Department of Chemistry DENMARK
| | | | - Lars Hemmingsen
- University of Copenhagen: Kobenhavns Universitet Department of Chemistry DENMARK
| | - Monika Stachura
- TRIUMF Life Sciences Division 4004 Wesbrook Mall V6T 2A3 Vancouver CANADA
| |
Collapse
|
8
|
Goli M, Shahbazian S. Two-component density functional theory for muonic molecules: Inclusion of the electron–positive muon correlation functional. J Chem Phys 2022; 156:044104. [DOI: 10.1063/5.0077179] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Mohammad Goli
- School of Nano Science, Institute for Research in Fundamental Sciences (IPM), Tehran 19395-5531, Iran
| | - Shant Shahbazian
- Department of Physics, Shahid Beheshti University, Evin, Tehran, Iran
| |
Collapse
|
9
|
Ito S, Akama H, Ueta Y, McKenzie I, Kojima KM. Muonium Addition to the Radicalic Carbon in 1,3-Diphosphacyclobutane-2,4-diyl. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2021. [DOI: 10.1246/bcsj.20210352] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Shigekazu Ito
- Department of Applied Chemistry, School of Materials and Chemical Technology, Tokyo Institute of Technology, 2-12-1-H113, Ookayama, Meguro-ku, Tokyo 152-8552, Japan
| | - Hikaru Akama
- Department of Applied Chemistry, School of Materials and Chemical Technology, Tokyo Institute of Technology, 2-12-1-H113, Ookayama, Meguro-ku, Tokyo 152-8552, Japan
| | - Yasuhiro Ueta
- Department of Applied Chemistry, School of Materials and Chemical Technology, Tokyo Institute of Technology, 2-12-1-H113, Ookayama, Meguro-ku, Tokyo 152-8552, Japan
| | - Iain McKenzie
- Centre for Molecular and Materials Science, TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3, Canada
| | - Kenji M. Kojima
- Centre for Molecular and Materials Science, TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3, Canada
| |
Collapse
|
10
|
McKenzie I, Scheuermann R, Tucker I, Mulley BP. Dynamics and local environment of an aromatic counterion bound to di-chain cationic surfactant bilayers studied by avoided level crossing muon spin resonance: evidence for counterion condensation. Phys Chem Chem Phys 2021; 23:25542-25549. [PMID: 34779806 DOI: 10.1039/d1cp04575j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Avoided level crossing muon spin resonance (ALC-μSR) has been used to study the reorientational dynamics of muon-spin-labelled 2,4,6-trimethylbenzoate (246TMB-) counterions and their interaction with DODMAC (dioctadecyldimethylammonium chloride) bilayers in the Lα and Lβ liquid crystalline states. The muoniated radical anion formed by the addition of muonium to the secondary carbons of the aromatic ring of 246TMB- is used as a local spin probe. The muon and methylene proton hyperfine parameters and the electron spin relaxation rate (λe) of the muoniated spin probe were determined as a function of temperature by modelling the ALC-μSR spectra with Monte Carlo numerical simulations. The observation of a Δ1 resonance indicates that 246TMB- is undergoing anisotropic motion and doesn't reside in the aqueous layer in either the Lα and Lβ phases. The lack of an abrupt change in the hyperfine parameters or λe when the system goes from the Lβ to the Lα lamellar liquid crystalline phases suggests that 246TMB- is located at the oil-water interface rather than within the bilayer. The hyperfine parameters indicate that 246TMB- is undergoing large amplitude reorientational motion about a preferred orientation resulting from the bilayer's electric field. The interaction between 246TMB- and the bilayer decreases and the amplitude of the wobbling-in-a-cone motion increases with increasing temperature. The temperature dependence of the electron spin relaxation rate indicates the barrier to reorientation is 41.7 kJ mol-1.
Collapse
Affiliation(s)
- Iain McKenzie
- Centre for Molecular and Materials Science, TRIUMF, Vancouver, Canada. .,Department of Chemistry, Simon Fraser University, Burnaby, Canada.,Department of Physics and Astronomy, University of Waterloo, Waterloo, Canada
| | - Robert Scheuermann
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institut, Villigen AG, Switzerland
| | - Ian Tucker
- 60 Springfields, Mickle Trafford, Chester, CH2 4EG, UK
| | - Brian P Mulley
- Centre for Molecular and Materials Science, TRIUMF, Vancouver, Canada. .,Department of Chemistry, University of Waterloo, Waterloo, Canada
| |
Collapse
|
11
|
Koshino K, Kojima KM, McKenzie I, Ito S. Muonium Addition to a peri-Trifluoromethylated 9-Phosphaanthracene Producing a High-Energy Paramagnetic π-Conjugated Fused Heterocycle. Angew Chem Int Ed Engl 2021; 60:24034-24038. [PMID: 34409713 DOI: 10.1002/anie.202109784] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Indexed: 01/08/2023]
Abstract
In this communication, we report muon spin rotation/resonance (μSR) studies for understanding radical reactivity of 10-mesityl-1,8-bis(trifluoromethyl)-9-phosphaanthracene. Transverse-field muon spin rotation (TF-μSR) and muon avoided level-crossing resonance (μLCR) measurements successfully visualized a paramagnetic species produced by regioselective addition of muonium (Mu) to the skeletal phosphorus atom. Density functional theory (DFT) calculations for the P-muoniation product suggested two possible isomers. Whereas the most stable isomer including the envelope-type phosphorus heterocycle shows considerably different hyperfine coupling constants (hfcs) from those of the TF-μSR and μLCR, the metastable structure accompanying the almost planar tricyclic π-conjugated skeleton could simulate the experimentally determined hfcs. The metastable planar π-conjugated paramagnetic tricyclic-fused skeleton is promoted by the larger zero-point energy due to the light muon (μ+ ), one ninth of the proton mass.
Collapse
Affiliation(s)
- Kota Koshino
- Department of Applied Chemistry, School of Materials and Chemical Technology, Tokyo Institute of Technology, 2-12-1-H113 Ookayama, Meguro-ku, Tokyo, 152-8552, Japan.,Present address: Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore
| | - Kenji M Kojima
- Centre for Molecular and Materials Science, TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3, Canada
| | - Iain McKenzie
- Centre for Molecular and Materials Science, TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3, Canada
| | - Shigekazu Ito
- Department of Applied Chemistry, School of Materials and Chemical Technology, Tokyo Institute of Technology, 2-12-1-H113 Ookayama, Meguro-ku, Tokyo, 152-8552, Japan
| |
Collapse
|
12
|
Koshino K, Kojima KM, McKenzie I, Ito S. Muonium Addition to a
peri
‐Trifluoromethylated 9‐Phosphaanthracene Producing a High‐Energy Paramagnetic π‐Conjugated Fused Heterocycle. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202109784] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Kota Koshino
- Department of Applied Chemistry School of Materials and Chemical Technology Tokyo Institute of Technology 2-12-1-H113 Ookayama, Meguro-ku Tokyo 152-8552 Japan
- Present address: Division of Chemistry and Biological Chemistry School of Physical and Mathematical Sciences Nanyang Technological University Singapore 637371 Singapore
| | - Kenji M. Kojima
- Centre for Molecular and Materials Science TRIUMF 4004 Wesbrook Mall Vancouver BC V6T 2A3 Canada
| | - Iain McKenzie
- Centre for Molecular and Materials Science TRIUMF 4004 Wesbrook Mall Vancouver BC V6T 2A3 Canada
| | - Shigekazu Ito
- Department of Applied Chemistry School of Materials and Chemical Technology Tokyo Institute of Technology 2-12-1-H113 Ookayama, Meguro-ku Tokyo 152-8552 Japan
| |
Collapse
|
13
|
Scollon M, Percival PW. Free Radicals Formed by H Atom Addition to Allenes as Determined by Muon Spin Spectroscopy. J Phys Chem A 2020; 124:11086-11092. [DOI: 10.1021/acs.jpca.0c09777] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Myles Scollon
- Department of Chemistry and TRIUMF, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
| | - Paul W. Percival
- Department of Chemistry and TRIUMF, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
| |
Collapse
|
14
|
Prando G, Perego J, Negroni M, Riccò M, Bracco S, Comotti A, Sozzani P, Carretta P. Molecular Rotors in a Metal-Organic Framework: Muons on a Hyper-Fast Carousel. NANO LETTERS 2020; 20:7613-7618. [PMID: 32870690 PMCID: PMC8011913 DOI: 10.1021/acs.nanolett.0c03140] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Revised: 08/31/2020] [Indexed: 06/11/2023]
Abstract
Using muon-spin spectroscopy, we study the exceptional dynamical properties of rotating molecular struts engineered within a Zn-based metal-organic framework at cryogenic temperatures, where the internal motions of almost any other organic substance are quenched. Muon-spin spectroscopy is particularly suited for this aim, as the experimental evidence suggests several implantation sites for the muons, among which at least one directly onto the rotating moiety. The dynamics of the molecular rotors are characterized by the exceptionally low activation energy EA ∼ 30 cal mol-1. At the same time, we evidence a highly unusual temperature dependence of the dipolar interaction of muons with nuclear magnetic moments on the rotors, suggesting a complex influence of the rotations on the muon implantation and diffusion.
Collapse
Affiliation(s)
- Giacomo Prando
- Department
of Physics, University of Pavia, I-27100 Pavia, Italy
| | - Jacopo Perego
- Department
of Materials Science, University of Milano
Bicocca, I-20125 Milano, Italy
| | - Mattia Negroni
- Department
of Materials Science, University of Milano
Bicocca, I-20125 Milano, Italy
| | - Mauro Riccò
- Department
of Mathematical, Physical and Information Sciences, University of Parma, I-43124 Parma, Italy
| | - Silvia Bracco
- Department
of Materials Science, University of Milano
Bicocca, I-20125 Milano, Italy
| | - Angiolina Comotti
- Department
of Materials Science, University of Milano
Bicocca, I-20125 Milano, Italy
| | - Piero Sozzani
- Department
of Materials Science, University of Milano
Bicocca, I-20125 Milano, Italy
| | - Pietro Carretta
- Department
of Physics, University of Pavia, I-27100 Pavia, Italy
| |
Collapse
|
15
|
Samedov K, Heider Y, Cai Y, Willmes P, Mühlhausen D, Huch V, West R, Scheschkewitz D, Percival PW. Free Radical Chemistry of Phosphasilenes. Angew Chem Int Ed Engl 2020; 59:16007-16012. [PMID: 32488930 PMCID: PMC7540504 DOI: 10.1002/anie.202006289] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 05/30/2020] [Indexed: 11/25/2022]
Abstract
Understanding the characteristics of radicals formed from silicon-containing heavy analogues of alkenes is of great importance for their application in radical polymerization. Steric and electronic substituent effects in compounds such as phosphasilenes not only stabilize the Si=P double bond, but also influence the structure and species of the formed radicals. Herein we report our first investigations of radicals derived from phosphasilenes with Mes, Tip, Dur, and NMe2 substituents on the P atom, using muon spin spectroscopy and DFT calculations. Adding muonium (a light isotope of hydrogen) to phosphasilenes reveals that: a) the electron-donor NMe2 and the bulkiest Tip-substituted phosphasilenes form several muoniated radicals with different rotamer conformations; b) bulky Dur-substituted phosphasilene forms two radicals (Si- and P-centred); and c) Mes-substituted phosphasilene mainly forms one species of radical, at the P centre. These significant differences result from intramolecular substituent effects.
Collapse
Affiliation(s)
- Kerim Samedov
- Beijing Advanced Innovation Center for Soft Matter Science and EngineeringBeijing University of Chemical TechnologyBeijing100029China
- Department of ChemistryUniversity of British Columbia2036 Main MallVancouverBCV6T 1Z1Canada
| | - Yannic Heider
- Krupp-Chair for General and Inorganic ChemistrySaarland UniversityCampus, C4.166123SaarbrückenGermany
| | - Yuanjing Cai
- Beijing Advanced Innovation Center for Soft Matter Science and EngineeringBeijing University of Chemical TechnologyBeijing100029China
| | - Philipp Willmes
- Krupp-Chair for General and Inorganic ChemistrySaarland UniversityCampus, C4.166123SaarbrückenGermany
| | - Daniel Mühlhausen
- Krupp-Chair for General and Inorganic ChemistrySaarland UniversityCampus, C4.166123SaarbrückenGermany
| | - Volker Huch
- Krupp-Chair for General and Inorganic ChemistrySaarland UniversityCampus, C4.166123SaarbrückenGermany
| | - Robert West
- Department of ChemistryUniversity of Wisconsin-Madison1101 University AvenueMadisonWI53706USA
| | - David Scheschkewitz
- Krupp-Chair for General and Inorganic ChemistrySaarland UniversityCampus, C4.166123SaarbrückenGermany
| | - Paul W. Percival
- Department of ChemistrySimon Fraser University8888 University DriveBurnabyBCV5A 1S6Canada
- Centre for Molecular and Materials Science, TRIUMF4004 Wesbrook MallVancouverBCV6T 2A3Canada
| |
Collapse
|
16
|
Samedov K, Heider Y, Cai Y, Willmes P, Mühlhausen D, Huch V, West R, Scheschkewitz D, Percival PW. Chemie freier Radikale von Phosphasilenen. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202006289] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Kerim Samedov
- Beijing Advanced Innovation Center for Soft Matter Science and Engineering Beijing University of Chemical Technology Peking 100029 China
- Department of Chemistry University of British Columbia 2036 Main Mall Vancouver BC V6T 1Z1 Kanada
| | - Yannic Heider
- Krupp-Lehrstuhl für Allgemeine und Anorganische Chemie Universität des Saarlandes Campus, C4.1 66123 Saarbrücken Deutschland
| | - Yuanjing Cai
- Beijing Advanced Innovation Center for Soft Matter Science and Engineering Beijing University of Chemical Technology Peking 100029 China
| | - Philipp Willmes
- Krupp-Lehrstuhl für Allgemeine und Anorganische Chemie Universität des Saarlandes Campus, C4.1 66123 Saarbrücken Deutschland
| | - Daniel Mühlhausen
- Krupp-Lehrstuhl für Allgemeine und Anorganische Chemie Universität des Saarlandes Campus, C4.1 66123 Saarbrücken Deutschland
| | - Volker Huch
- Krupp-Lehrstuhl für Allgemeine und Anorganische Chemie Universität des Saarlandes Campus, C4.1 66123 Saarbrücken Deutschland
| | - Robert West
- Department of Chemistry University of Wisconsin-Madison 1101 University Avenue Madison WI 53706 USA
| | - David Scheschkewitz
- Krupp-Lehrstuhl für Allgemeine und Anorganische Chemie Universität des Saarlandes Campus, C4.1 66123 Saarbrücken Deutschland
| | - Paul W. Percival
- Department of Chemistry Simon Fraser University 8888 University Drive Burnaby BC V5A 1S6 Kanada
- Centre for Molecular and Materials Science, TRIUMF 4004 Wesbrook Mall Vancouver BC V6T 2A3 Kanada
| |
Collapse
|
17
|
McKenzie I, Cordoni-Jordan D, Cannon J, Cottrell SP. Dynamics of polystyrene probed by muon spin spectroscopy. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 33:065102. [PMID: 33325374 DOI: 10.1088/1361-648x/abc4ca] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Muon spin spectroscopic measurements were made on atactic low-molecular-weight (LMW) (1.3 kg mol-1) and high-molecular-weight (HMW) (202 kg mol-1) polystyrene. Muoniated cyclohexadienyl radicals, which are formed by muonium addition to the phenyl side groups, are used as local probes of bulk dynamics. Muon spin relaxation is caused by the secondary γ-relaxation process, which involves motion of the phenyl rings, and is sensitive to the glass transition. The activation energy of the γ-relaxation process in the rubbery state is 0.60(2) eV in the HMW sample and 0.37(3) eV in the LMW sample.
Collapse
Affiliation(s)
- Iain McKenzie
- Centre for Molecular and Material Science, TRIUMF, Vancouver, BC V6T 2A3, Canada
- Department of Chemistry, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
- Department of Physics, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | | | - Joseph Cannon
- School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA, United Kingdom
| | - Stephen P Cottrell
- ISIS, STFC Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, United Kingdom
| |
Collapse
|
18
|
Aramini M, Cottrell S, Peck J, Yokoyama K. Next generation equipment for muon chemistry research. JOURNAL OF NEUTRON RESEARCH 2020. [DOI: 10.3233/jnr-190118] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Affiliation(s)
- M. Aramini
- ISIS Facility, STFC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX, UK
| | - S.P. Cottrell
- ISIS Facility, STFC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX, UK
| | - J.N.T. Peck
- ISIS Facility, STFC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX, UK
| | - K. Yokoyama
- ISIS Facility, STFC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX, UK
| |
Collapse
|
19
|
Ito S. Investigation of Organic Molecules Using Elementary Subatomic Particle: Muon Spin Spectroscopy for Reaction Analysis of the Open-Shell Singlet Heterocycle. J SYN ORG CHEM JPN 2019. [DOI: 10.5059/yukigoseikyokaishi.77.800] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Shigekazu Ito
- Department of Chemical Science and Engineering, School of Materials and Chemical Technology, Tokyo Institute of Technology
| |
Collapse
|
20
|
McKenzie I. Hydrogen-Atom Addition to Nucleobases in the Solid State: Characterization of the Corresponding Muoniated Radicals Using μSR. J Phys Chem B 2019; 123:4540-4549. [PMID: 31095384 DOI: 10.1021/acs.jpcb.9b02930] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The radicals formed by muonium (Mu) addition to four nucleobases (adenine, guanine, cytosine, and thymine) have been characterized by avoided level-crossing muon spin resonance (ALC-μSR). Mu is considered to be a light isotope of the hydrogen atom, and the muoniated radicals observed by ALC-μSR are isotopomers of the radicals initially produced by H addition to the nucleobases. The observed radicals have been assigned by considering the relative energies of the possible radicals reported in the literature and comparing the experimental muon and proton hyperfine coupling constants with values from previously reported electron paramagnetic resonance and ab initio calculations that have been scaled to account for the larger magnetic moment of the muon and its lighter mass compared with the proton. Mu addition is observed to occur only at secondary carbons of the purine rings in adenine and guanine. Mu adds to C8 and C2 of adenine with the relative amount being ∼70:30%, and Mu adds exclusively to C8 of guanine. Mu addition is predominantly to the secondary carbons of the pyrimidine ring in cytosine (C5 and C6 with relative yields ∼80:20%) with a small amount of addition at N3. Mu adds to both the secondary C6 and tertiary C5 in thymine with approximately equal yields as well as the O4 adduct being a minor product.
Collapse
Affiliation(s)
- Iain McKenzie
- Centre for Molecular and Materials Science , TRIUMF , 4004 Wesbrook Mall , Vancouver , British Columbia , Canada V6T 2A3.,Department of Chemistry , Simon Fraser University , 8888 University Drive , Burnaby , British Columbia , Canada V5A 1S6
| |
Collapse
|
21
|
Chandrasena L, Samedov K, McKenzie I, Mozafari M, West R, Gates DP, Percival PW. Free Radical Reactivity of a Phosphaalkene Explored Through Studies of Radical Isotopologues. Angew Chem Int Ed Engl 2019; 58:297-301. [PMID: 30450733 DOI: 10.1002/anie.201810967] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2018] [Revised: 11/15/2018] [Indexed: 12/13/2022]
Abstract
Muonium (Mu), an H atom analogue, is employed to probe the addition of free radicals to the P=C bond of a phosphaalkene. Specifically, two unprecedented muoniated free radicals, MesP. -CMu(Me)2 (1 a, minor product) and MesPMu-C. Me2 (1 b, major product), were detected by muon spin spectroscopy (μSR) when a solution of MesP=CMe2 (1: Mes=2,4,6-trimethylphenyl) was exposed to a beam of positive muons (μ+ ). The μ+ serves as a source of Mu (that is, Mu=μ+ +e- ). To confirm the identity of the major product 1 b, its spectral features were compared to its isotopologue, MesPH-C. (Me)CH2 Mu (2 a). Conveniently, 2 a is the sole product of the reaction of MesPH(CMe=CH2 ) (2) with Mu. For all observed radicals, muon, proton, and phosphorus hyperfine coupling constants were determined by μSR and compared to DFT-calculated values.
Collapse
Affiliation(s)
- Lalangi Chandrasena
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada
| | - Kerim Samedov
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC, V6T 1Z1, Canada
| | - Iain McKenzie
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada.,Centre for Molecular and Materials Science, TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3, Canada
| | - Mina Mozafari
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada
| | - Robert West
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI, 53706, USA
| | - Derek P Gates
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC, V6T 1Z1, Canada
| | - Paul W Percival
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada
| |
Collapse
|
22
|
Chandrasena L, Samedov K, McKenzie I, Mozafari M, West R, Gates DP, Percival PW. Free Radical Reactivity of a Phosphaalkene Explored Through Studies of Radical Isotopologues. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201810967] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Lalangi Chandrasena
- Department of Chemistry; Simon Fraser University; 8888 University Drive Burnaby BC V5A 1S6 Canada
| | - Kerim Samedov
- Department of Chemistry; University of British Columbia; 2036 Main Mall Vancouver BC V6T 1Z1 Canada
| | - Iain McKenzie
- Department of Chemistry; Simon Fraser University; 8888 University Drive Burnaby BC V5A 1S6 Canada
- Centre for Molecular and Materials Science; TRIUMF; 4004 Wesbrook Mall Vancouver BC V6T 2A3 Canada
| | - Mina Mozafari
- Department of Chemistry; Simon Fraser University; 8888 University Drive Burnaby BC V5A 1S6 Canada
| | - Robert West
- Department of Chemistry; University of Wisconsin-Madison; 1101 University Avenue Madison WI 53706 USA
| | - Derek P. Gates
- Department of Chemistry; University of British Columbia; 2036 Main Mall Vancouver BC V6T 1Z1 Canada
| | - Paul W. Percival
- Department of Chemistry; Simon Fraser University; 8888 University Drive Burnaby BC V5A 1S6 Canada
| |
Collapse
|
23
|
Ito S, Ueta Y, Koshino K, Kojima KM, McKenzie I, Mikami K. Observation of a Metastable P-Heterocyclic Radical by Muonium Addition to a 1,3-Diphosphacyclobutane-2,4-diyl. Angew Chem Int Ed Engl 2018; 57:8608-8613. [PMID: 29790272 DOI: 10.1002/anie.201804306] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Revised: 05/22/2018] [Indexed: 12/13/2022]
Abstract
A 1,3-diphosphacyclobutane-2,4-diyl contains a unique unsaturated cyclic unit, and the presence of radical-type centers have been expected as a source of functionality. This study demonstrates that the P-heterocyclic singlet biradical captures muonium (Mu=[μ+ e- ]), the light isotope of a hydrogen radical, to generate an observable P-heterocyclic paramagnetic species. Investigation of a powder sample of 2,4-bis(2,4,6-tri-t-butylphenyl)-1-t-butyl-3-benzyl-1,3-diphosphacyclobutane-2,4-diyl using muon (avoided) level-crossing resonance (μLCR) spectroscopy revealed that muonium adds to the cyclic P2 C2 unit. The muon hyperfine coupling constant (Aμ ) indicated that the phosphorus atom bearing the t-butyl group trapped muonium to provide a metastable P-heterocyclic radical involving the ylidic MuP(<)=C moiety. The observed regioselective muonium addition correlates the canonical formula of 1,3-diphosphacyclobutane-2,4-diyl.
Collapse
Affiliation(s)
- Shigekazu Ito
- Department of Chemical Science and Engineering, School of Materials and Chemical Technology, Tokyo Institute of Technology, 2-12-1-H113 Ookayama, Meguro, Tokyo, 152-8552, Japan
| | - Yasuhiro Ueta
- Department of Chemical Science and Engineering, School of Materials and Chemical Technology, Tokyo Institute of Technology, 2-12-1-H113 Ookayama, Meguro, Tokyo, 152-8552, Japan
| | - Kota Koshino
- Department of Chemical Science and Engineering, School of Materials and Chemical Technology, Tokyo Institute of Technology, 2-12-1-H113 Ookayama, Meguro, Tokyo, 152-8552, Japan
| | - Kenji M Kojima
- Muon Science Laboratory, High Energy Accelerator Research Organization (KEK-IMSS), Tsukuba, Ibaraki, 305-0801, Japan
| | - Iain McKenzie
- Centre for Molecular and Materials Science, TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3, Canada
| | - Koichi Mikami
- Department of Chemical Science and Engineering, School of Materials and Chemical Technology, Tokyo Institute of Technology, 2-12-1-H113 Ookayama, Meguro, Tokyo, 152-8552, Japan
| |
Collapse
|
24
|
Goli M, Shahbazian S. Developing effective electronic-only coupled-cluster and Møller-Plesset perturbation theories for the muonic molecules. Phys Chem Chem Phys 2018; 20:16749-16760. [PMID: 29881845 DOI: 10.1039/c8cp02489h] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Recently we have proposed an effective Hartree-Fock (EHF) theory for the electrons of the muonic molecules that is formally equivalent to the HF theory within the context of the nuclear-electronic orbital theory [Phys. Chem. Chem. Phys., 2018, 20, 4466]. In the present report we extend the muon-specific effective electronic structure theory beyond the EHF level by introducing the effective second order Møller-Plesset perturbation theory (EMP2) and the effective coupled-cluster theory at single and double excitation levels (ECCSD) as well as an improved version including perturbative triple excitations (ECCSD(T)). These theories incorporate electron-electron correlation into the effective paradigm and through their computational implementation, a diverse set of small muonic species is considered as a benchmark at these post-EHF levels. A comparative computational study on this set demonstrates that the muonic bond length is in general non-negligibly longer than corresponding hydrogenic analogs. Next, the developed post-EHF theories are applied for the muoniated N-heterocyclic carbene/silylene/germylene and the muoniated triazolium cation revealing the relative stability of the sticking sites of the muon in each species. The computational results, in line with previously reported experimental data demonstrate that the muon generally prefers to attach to the divalent atom with carbeneic nature. A detailed comparison of these muonic adducts with the corresponding hydrogenic adducts reveals subtle differences that have already been overlooked.
Collapse
Affiliation(s)
- Mohammad Goli
- School of Nano Science, Institute for Research in Fundamental Sciences (IPM), 19395-5531, Tehran, Iran.
| | | |
Collapse
|
25
|
Ito S, Ueta Y, Koshino K, Kojima KM, McKenzie I, Mikami K. Observation of a Metastable P‐Heterocyclic Radical by Muonium Addition to a 1,3‐Diphosphacyclobutane‐2,4‐diyl. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201804306] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Shigekazu Ito
- Department of Chemical Science and Engineering School of Materials and Chemical Technology Tokyo Institute of Technology 2-12-1-H113 Ookayama Meguro Tokyo 152-8552 Japan
| | - Yasuhiro Ueta
- Department of Chemical Science and Engineering School of Materials and Chemical Technology Tokyo Institute of Technology 2-12-1-H113 Ookayama Meguro Tokyo 152-8552 Japan
| | - Kota Koshino
- Department of Chemical Science and Engineering School of Materials and Chemical Technology Tokyo Institute of Technology 2-12-1-H113 Ookayama Meguro Tokyo 152-8552 Japan
| | - Kenji M. Kojima
- Muon Science Laboratory High Energy Accelerator Research Organization (KEK-IMSS) Tsukuba Ibaraki 305-0801 Japan
| | - Iain McKenzie
- Centre for Molecular and Materials Science, TRIUMF 4004 Wesbrook Mall Vancouver BC V6T 2A3 Canada
| | - Koichi Mikami
- Department of Chemical Science and Engineering School of Materials and Chemical Technology Tokyo Institute of Technology 2-12-1-H113 Ookayama Meguro Tokyo 152-8552 Japan
| |
Collapse
|
26
|
McKenzie I. Radical addition to ruthenocene at low temperatures: characterization of ruthenocenyl radicals by μSR spectroscopy. CAN J CHEM 2018. [DOI: 10.1139/cjc-2017-0207] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The radicals formed by muonium (Mu) addition to ruthenocene at low temperature (4–200 K) have been characterized by transverse field muon spin rotation (TF-μSR) and avoided level crossing muon spin resonance (ALC-μSR) spectroscopy. The structures of the muoniated radicals have been identified by comparing the experimentally measured muon hyperfine coupling constants with values obtained from DFT calculations (UB3LYP/DGDZVP). Mu addition was observed at the ruthenium and at the cyclopentadiene (Cp) rings, both from the exterior and interior directions. Closer agreement between the DFT calculations and the experimental values are obtained if it is assumed the structures of the Mu adducts of the Cp rings are distorted due to interactions with neighbouring molecules. Changes in the ALC-μSR spectra with temperature indicated that the electron spin relaxation rate of the Cp adducts increases with temperature; however, the specific spin relaxation mechanism is unknown.
Collapse
Affiliation(s)
- Iain McKenzie
- Centre for Molecular and Materials Science, TRIUMF, Vancouver, BC V6T 2A3, Canada, and Department of Chemistry, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
- Centre for Molecular and Materials Science, TRIUMF, Vancouver, BC V6T 2A3, Canada, and Department of Chemistry, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
| |
Collapse
|
27
|
Rayka M, Goli M, Shahbazian S. Toward a muon-specific electronic structure theory: effective electronic Hartree-Fock equations for muonic molecules. Phys Chem Chem Phys 2018; 20:4466-4477. [PMID: 29372727 DOI: 10.1039/c7cp07599e] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
An effective set of Hartree-Fock (HF) equations are derived for electrons of muonic systems, i.e., molecules containing a positively charged muon, conceiving the muon as a quantum oscillator, which are completely equivalent to the usual two-component HF equations used to derive stationary states of the muonic molecules. In these effective equations, a non-Coulombic potential is added to the orthodox coulomb and exchange potential energy terms, which describes the interaction of the muon and the electrons effectively and is optimized during the self-consistent field cycles. While in the two-component HF equations a muon is treated as a quantum particle, in the effective HF equations it is absorbed into the effective potential and practically transformed into an effective potential field experienced by electrons. The explicit form of the effective potential depends on the nature of muon's vibrations and is derivable from the basis set used to expand the muonic spatial orbital. The resulting effective Hartree-Fock equations are implemented computationally and used successfully, as a proof of concept, in a series of muonic molecules containing all atoms from the second and third rows of the Periodic Table. To solve the algebraic version of the equations muon-specific Gaussian basis sets are designed for both muon and surrounding electrons and it is demonstrated that the optimized exponents are quite distinct from those derived for the hydrogen isotopes. The developed effective HF theory is quite general and in principle can be used for any muonic system while it is the starting point for a general effective electronic structure theory that incorporates various types of quantum correlations into the muonic systems beyond the HF equations.
Collapse
Affiliation(s)
- Milad Rayka
- Department of Physics and Department of Physical and Computational Chemistry, Shahid Beheshti University, G. C., Evin, P.O. Box 19395-4716, Tehran, 19839, Iran.
| | | | | |
Collapse
|
28
|
Mozafari M, Chandrasena L, McKenzie I, Samedov K, Percival PW. Characterization of free radicals in clathrate hydrates of pyrrole, thiophene, and isoxazole by muon spin spectroscopy. CAN J CHEM 2018. [DOI: 10.1139/cjc-2017-0313] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Gas hydrates have long been of interest to the petrochemical industry, but there has been growing interest in potential applications for carbon dioxide sequestration and hydrogen storage. This has prompted many fundamental studies of structure and host–guest interactions, but there has been relatively little investigation of chemical reactions of the guest molecules. In previous work, we have shown that it is possible to use muon spin spectroscopy to characterize H atom like muonium and muoniated free radicals formed in clathrate hydrates. Muonium (Mu) forms in clathrate hydrates of cyclopentane and tetrahydrofuran, whereas furan and its dihydro derivatives form radicals. The current work extends studies to clathrates hydrates of other five-membered heterocycles: thiophene, pyrrole, and isoxazole. All form structure II hydrates. In addition to the clathrates, pure liquid samples of the heterocycles were studied to aid in the assignment of radical signals and for comparison with the enclathrated radicals. Similar to furan, two distinct radicals are formed when Mu reacts with thiophene and pyrrole. However, only one muoniated radical was detected from isoxazole. Muon, proton, and nitrogen hyperfine constants were determined and compared with values predicted by DFT calculations to aid the structure assignments. The results show that Mu adds preferentially to the carbon adjacent to the heteroatom in thiophene and pyrrole and to the carbon adjacent to oxygen in isoxazole. The same radicals are formed in clathrates, but the spectra have broader signals, suggesting slower tumbling. Furthermore, additional signals in the avoided level-crossing spectra indicate anisotropy consistent with restricted motion of the radicals in the clathrate cages.
Collapse
Affiliation(s)
- Mina Mozafari
- Department of Chemistry and TRIUMF, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
| | - Lalangi Chandrasena
- Department of Chemistry and TRIUMF, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
| | - Iain McKenzie
- Department of Chemistry and TRIUMF, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
| | - Kerim Samedov
- Department of Chemistry, University of British Columbia, Vancouver, BC V6T 1Z1, Canada
| | - Paul W. Percival
- Department of Chemistry and TRIUMF, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
| |
Collapse
|
29
|
McKenzie I, Cottrell SP. Microscopic muon dynamics in the polymer electrolyte poly(ethylene oxide). Phys Rev E 2017; 96:012502. [PMID: 29347120 DOI: 10.1103/physreve.96.012502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Indexed: 06/07/2023]
Abstract
The microscopic dynamics of protons (H^{+}) in poly(ethylene oxide) (PEO) have been investigated through a study of implanted positive muons (Mu^{+}), which can be considered a light proton analog. The exponential decay of the muon spin polarization in zero magnetic field indicated that Mu^{+} hopping is in the fast fluctuation limit between 140 and 310 K and the relaxation rate was found to be sensitive to the glass transition. Mu^{+} dynamics in PEO was monitored via the relaxation of the muon spin polarization in a transverse field of 10 mT. Activated hopping of Mu^{+} was observed above the glass transition temperature with an activation barrier of 122±1 meV. The temperature dependence of the diamagnetic muon polarization in PEO can be explained by diffusion of radiolytic electrons.
Collapse
Affiliation(s)
- Iain McKenzie
- TRIUMF, Vancouver, B.C., Canada, V6T 2A3
- Department of Chemistry, Simon Fraser University, Burnaby, B.C. Canada, V5A 1S6
| | - Stephen P Cottrell
- ISIS, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX11 0QX, United Kingdom
| |
Collapse
|
30
|
McKenzie I, Scheuermann R, Tucker I. Partitioning of 2-phenylethanol and limonene cosurfactants in C 12E 4. Phys Chem Chem Phys 2017; 19:9551-9557. [PMID: 28345720 DOI: 10.1039/c7cp00668c] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Avoided level-crossing muon spin resonance (ALC-μSR) has been used to study the dynamics and local environment of spin probes formed by muonium (Mu) addition to 2-phenylethanol (PEA) and limonene (1-methyl-4-(1-methylethenyl)-cyclohexene) in an aqueous dispersion of the nonionic surfactant C12E4 (tetra(ethylene glycol) n-dodecyl ether). The spin probes derived from both cosurfactants reside within the micelles in the L1 phase and the bilayers in the Lα phase rather than in the aqueous region. The local polarity measured by the different isomers of the Mu adducts of PEA suggests there is a water gradient within the micelles and bilayers. Slow rotation of the micelles broadened the Δ1 resonances with increasing temperature in the L1 phase while narrower Δ1 resonances were observed in the Lα phase due to the rapid rotation of the spin probes around a preferred axis, which was wobbling within a cone.
Collapse
Affiliation(s)
- Iain McKenzie
- Centre for Molecular and Materials Science, TRIUMF, Vancouver, BC, Canada. and Department of Chemistry, Simon Fraser University, Burnaby, BC, Canada
| | - Robert Scheuermann
- Laboratory for Muon Spectroscopy, Paul Scherrer Institute, Villigen AG, Switzerland
| | - Ian Tucker
- Unilever Research and Development, Port Sunlight, Wirral, UK
| |
Collapse
|
31
|
Wright JA, Peck JNT, Cottrell SP, Jablonskytė A, Oganesyan VS, Pickett CJ, Jayasooriya UA. Muonium Chemistry at Diiron Subsite Analogues of [FeFe]-Hydrogenase. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201607109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Joseph A. Wright
- Energy Materials Laboratory; School of Chemistry; University of East Anglia; Norwich NR4 7TJ UK
| | - Jamie N. T. Peck
- Energy Materials Laboratory; School of Chemistry; University of East Anglia; Norwich NR4 7TJ UK
- Rutherford Appleton Laboratory; Harwell Oxford Didcot OX11 0QX UK
| | | | - Aušra Jablonskytė
- Energy Materials Laboratory; School of Chemistry; University of East Anglia; Norwich NR4 7TJ UK
| | - Vasily S. Oganesyan
- Energy Materials Laboratory; School of Chemistry; University of East Anglia; Norwich NR4 7TJ UK
| | - Christopher J. Pickett
- Energy Materials Laboratory; School of Chemistry; University of East Anglia; Norwich NR4 7TJ UK
| | - Upali A. Jayasooriya
- Energy Materials Laboratory; School of Chemistry; University of East Anglia; Norwich NR4 7TJ UK
| |
Collapse
|
32
|
Wright JA, Peck JNT, Cottrell SP, Jablonskytė A, Oganesyan VS, Pickett CJ, Jayasooriya UA. Muonium Chemistry at Diiron Subsite Analogues of [FeFe]-Hydrogenase. Angew Chem Int Ed Engl 2016; 55:14580-14583. [PMID: 27739628 PMCID: PMC5484327 DOI: 10.1002/anie.201607109] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Indexed: 11/29/2022]
Abstract
The chemistry of metal hydrides is implicated in a range of catalytic processes at metal centers. Gaining insight into the formation of such sites by protonation and/or electronation is therefore of significant value in fully exploiting the potential of such systems. Here, we show that the muonium radical (Mu.), used as a low isotopic mass analogue of hydrogen, can be exploited to probe the early stages of hydride formation at metal centers. Mu. undergoes the same chemical reactions as H. and can be directly observed due to its short lifetime (in the microseconds) and unique breakdown signature. By implanting Mu. into three models of the [FeFe]‐hydrogenase active site we have been able to detect key muoniated intermediates of direct relevance to the hydride chemistry of these systems.
Collapse
Affiliation(s)
- Joseph A Wright
- Energy Materials Laboratory, School of Chemistry, University of East Anglia, Norwich, NR4 7TJ, UK
| | - Jamie N T Peck
- Energy Materials Laboratory, School of Chemistry, University of East Anglia, Norwich, NR4 7TJ, UK.,Rutherford Appleton Laboratory, Harwell Oxford, Didcot, OX11 0QX, UK
| | | | - Aušra Jablonskytė
- Energy Materials Laboratory, School of Chemistry, University of East Anglia, Norwich, NR4 7TJ, UK
| | - Vasily S Oganesyan
- Energy Materials Laboratory, School of Chemistry, University of East Anglia, Norwich, NR4 7TJ, UK
| | - Christopher J Pickett
- Energy Materials Laboratory, School of Chemistry, University of East Anglia, Norwich, NR4 7TJ, UK
| | - Upali A Jayasooriya
- Energy Materials Laboratory, School of Chemistry, University of East Anglia, Norwich, NR4 7TJ, UK
| |
Collapse
|
33
|
Mozafari M, Brodovitch JC, Chandrasena L, Percival PW. Characterization of Free Radicals in Clathrate Hydrates of Furan, 2,3-Dihydrofuran, and 2,5-Dihydrofuran by Muon Spin Spectroscopy. J Phys Chem A 2016; 120:8521-8528. [PMID: 27726399 DOI: 10.1021/acs.jpca.6b08653] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In addition to their importance as abundant hydrocarbon deposits in nature, clathrate hydrates are being studied as potential media for hydrogen and carbon dioxide storage and as "nano-reactors" for small molecules. However, little is known about the behavior of reactive species in such materials. We have employed muon spin spectroscopy to characterize various organic free radicals that reside as isolated guests in structure II clathrates. The radicals are formed by reaction of atomic muonium (Mu) with the guest molecules furan and two isomeric dihydrofurans. Muonium is essentially a light isotope of hydrogen and adds to unsaturated molecules in the same manner as H. We have determined muon and proton hyperfine coupling constants for the muoniated radicals formed in the clathrates and also in neat liquids at the same temperature. DFT calculations were used to guide the spectral assignments and distinguish between competing radical products for Mu addition to furan and 2,3-dihydrofuran. Relative signal amplitudes provide yields and thus the relative reactivities of the C4 and C5 addition sites in these molecules. Spectral features, hyperfine constants, and reactivities all indicate that the radicals do not tumble freely in the clathrate cages in the same way that they do in liquids.
Collapse
Affiliation(s)
- Mina Mozafari
- Department of Chemistry and TRIUMF, Simon Fraser University , Burnaby, BC V5A 1S6, Canada
| | - Jean-Claude Brodovitch
- Department of Chemistry and TRIUMF, Simon Fraser University , Burnaby, BC V5A 1S6, Canada
| | - Lalangi Chandrasena
- Department of Chemistry and TRIUMF, Simon Fraser University , Burnaby, BC V5A 1S6, Canada
| | - Paul W Percival
- Department of Chemistry and TRIUMF, Simon Fraser University , Burnaby, BC V5A 1S6, Canada
| |
Collapse
|
34
|
Jayasooriya UA, Clayden NJ, Steytler DC, Oganesyan VS, Peck JNT, Khasanov R, Scheuermann R, Stoykov A. Rate of Molecular Transfer of Allyl Alcohol across an AOT Surfactant Layer Using Muon Spin Spectroscopy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:664-672. [PMID: 26716949 DOI: 10.1021/acs.langmuir.5b03482] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The transfer rate of a probe molecule across the interfacial layer of a water-in-oil (w/o) microemulsion was investigated using a combination of transverse field muon spin rotation (TF-μSR), avoided level crossing muon spin resonance (ALC-μSR), and Monte Carlo simulations. Reverse microemulsions consist of nanometer-sized water droplets dispersed in an apolar solvent separated by a surfactant monolayer. Although the thermodynamic, static model of these systems has been well described, our understanding of their dynamics is currently incomplete. For example, what is the rate of solute transfer between the aqueous and apolar solvents, and how this is influenced by the structure of the interface? With an appropriate choice of system and probe molecule, μSR offers a unique opportunity to directly probe these interfacial transfer dynamics. Here, we have employed a well characterized w/o microemulsion stabilized by bis(2-ethylhexyl) sodium sulfosuccinate (Aerosol OT), with allyl alcohol (CH2═CH-CH2-OH, AA) as the probe. Resonances due to both muoniated radicals, CMuH2-C*H-CH2-OH and C*H2-CHMu-CH2-OH, were observed with the former being the dominant species. All resonances displayed solvent dependence, with those in the microemulsion observed as a single resonance located at intermediate magnetic fields to those present in either of the pure solvents. Observation of a single resonance is strong evidence for interfacial transfer being in the fast exchange limit. Monte Carlo calculations of the ΔM = 0 ALC resonances are consistent with the experimental data, indicating exchange rates greater than 10(9) s(-1), placing the rate of interfacial transfer at the diffusion limit.
Collapse
Affiliation(s)
- Upali A Jayasooriya
- School of Chemistry, University of East Anglia , Norwich NR4 7TJ, United Kingdom
| | - Nigel J Clayden
- School of Chemistry, University of East Anglia , Norwich NR4 7TJ, United Kingdom
| | - David C Steytler
- School of Chemistry, University of East Anglia , Norwich NR4 7TJ, United Kingdom
| | - Vasily S Oganesyan
- School of Chemistry, University of East Anglia , Norwich NR4 7TJ, United Kingdom
| | - Jamie N T Peck
- School of Chemistry, University of East Anglia , Norwich NR4 7TJ, United Kingdom
| | - Rustem Khasanov
- Laboratory for Muon-Spin Spectroscopy, Paul Scherrer Institut , WBBA/120, CH-5232 Villigen PSI, Switzerland
| | - Robert Scheuermann
- Laboratory for Muon-Spin Spectroscopy, Paul Scherrer Institut , WBBA/120, CH-5232 Villigen PSI, Switzerland
| | - Alexey Stoykov
- Laboratory for Muon-Spin Spectroscopy, Paul Scherrer Institut , WBBA/120, CH-5232 Villigen PSI, Switzerland
| |
Collapse
|
35
|
Long AK, Fawcett JA, Clyburne JAC, Pye CC. RADMAP: Simple probes for rapid assessment of complex reactivity: A method and case studies on the reaction of hydrogen atoms with unsaturated organic molecules. J Mol Graph Model 2016; 64:147-152. [PMID: 26851865 DOI: 10.1016/j.jmgm.2016.01.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Revised: 12/07/2015] [Accepted: 01/10/2016] [Indexed: 11/30/2022]
Abstract
RADMAP, an open source program, allows for rapid analysis and visualization of the earliest stages of reactions between any molecule and a monoatomic probe (i.e., H*, H(+), H(-), Br*, or any other monoatomic species) using ab initio methods. This program creates non-planar potential energy surfaces of the initial interaction between a molecule of interest and the monoatomic probe. These surfaces can be used to both predict the site of addition as well as provide a qualitative estimate for the relative proportion of the formation of adducts; therefore, it gives insight into both the reactivity and the kinetic stability of a molecule. The program presents a way to quickly predict the number of signals anticipated in transverse field muon spin resonance spectra as well as their relative intensities.
Collapse
Affiliation(s)
- Andrew K Long
- Atlantic Centre for Green Chemistry, Department of Chemistry, Saint Mary's University, Halifax, NS B3H 3C3, Canada
| | - Jason A Fawcett
- Atlantic Centre for Green Chemistry, Department of Chemistry, Saint Mary's University, Halifax, NS B3H 3C3, Canada
| | - Jason A C Clyburne
- Atlantic Centre for Green Chemistry, Department of Chemistry, Saint Mary's University, Halifax, NS B3H 3C3, Canada
| | - Cory C Pye
- Atlantic Centre for Green Chemistry, Department of Chemistry, Saint Mary's University, Halifax, NS B3H 3C3, Canada.
| |
Collapse
|
36
|
Goli M, Shahbazian S. Where to place the positive muon in the Periodic Table? Phys Chem Chem Phys 2015; 17:7023-37. [PMID: 25684734 DOI: 10.1039/c4cp06006g] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In a recent study it was suggested that the positively charged muon is capable of forming its own "atoms in molecules" (AIM) in the muonic hydrogen-like molecules, composed of two electrons, a muon and one of the hydrogen's isotopes, thus deserves to be placed in the Periodic Table [Phys. Chem. Chem. Phys., 2014, 16, 6602]. In the present report, the capacity of the positively charged muon in forming its own AIM is considered in a large set of molecules replacing muons with all protons in the hydrides of the second and third rows of the Periodic Table. Accordingly, in a comparative study the wavefunctions of both sets of hydrides and their muonic congeners are first derived beyond the Born-Oppenheimer (BO) paradigm, assuming protons and muons as quantum waves instead of clamped particles. Then, the non-BO wavefunctions are used to derive the AIM structures of both hydrides and muonic congeners within the context of the multi-component quantum theory of atoms in molecules. The results of the analysis demonstrate that muons are generally capable of forming their own atomic basins and the properties of these basins are not fundamentally different from those AIM containing protons. Particularly, the bonding modes in the muonic species seem to be qualitatively similar to their congener hydrides and no new bonding model is required to describe the bonding of muons to a diverse set of neighboring atoms. All in all, the positively charged muon is similar to a proton from the structural and bonding viewpoint and deserves to be placed in the same box of hydrogen in the Periodic Table. This conclusion is in line with a large body of studies on the chemical kinetics of the muonic molecules portraying the positively charged muon as a lighter isotope of hydrogen.
Collapse
Affiliation(s)
- Mohammad Goli
- Faculty of Chemistry, Shahid Beheshti University, G. C., Evin, P.O. Box 19395-4716, Tehran, 19839, Iran.
| | | |
Collapse
|
37
|
McKenzie I, Daley CR, Kiefl RF, Levy CDP, MacFarlane WA, Morris GD, Pearson MR, Wang D, Forrest JA. Enhanced high-frequency molecular dynamics in the near-surface region of polystyrene thin films observed with β-NMR. SOFT MATTER 2015; 11:1755-1761. [PMID: 25605007 DOI: 10.1039/c4sm02245a] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
β-detected nuclear spin relaxation of (8)Li(+) has been used to probe the depth dependence of molecular dynamics in high- and low-molecular-weight deuterated polystyrene. The average nuclear spin-lattice relaxation rate, 1/T(avg)(1), is a measure of the spectral density of the polymer motion at the Larmor frequency (41 MHz at 6.55 T). In both samples, 1/T(avg)(1) is depth independent below ∼200 K but above this temperature it decreases approximately exponentially with distance from the free surface, returning to bulk behavior for depths greater than ∼10 nm. This is direct evidence for a region near the free surface with enhanced molecular dynamics compared with the bulk. The effective thickness of the surface region increases with increasing temperature and is finite even above the glass transition. These results present challenges for the current understanding of dynamics near the surface of polymer glasses.
Collapse
|
38
|
Brodovitch JC, Addison-Jones B, Ghandi K, McKenzie I, Percival PW. Proton, muon and13C hyperfine coupling constants of C60X and C70X (X = H, Mu). Phys Chem Chem Phys 2015; 17:1755-62. [DOI: 10.1039/c4cp04899g] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Four of the five possible C70H radicals are formed when H atoms add to fullerene C70. Their13C hyperfine constants reveal the extent of their unpaired spin distributions.
Collapse
Affiliation(s)
| | | | - Khashayar Ghandi
- Department of Chemistry
- Simon Fraser University
- Burnaby BC V5A 1S6
- Canada
| | - Iain McKenzie
- Department of Chemistry
- Simon Fraser University
- Burnaby BC V5A 1S6
- Canada
- TRIUMF
| | - Paul W. Percival
- Department of Chemistry
- Simon Fraser University
- Burnaby BC V5A 1S6
- Canada
- TRIUMF
| |
Collapse
|
39
|
|
40
|
West R, Samedov K, Percival PW. Silicon meets cyclotron: muon spin resonance of organosilicon radicals. Chemistry 2014; 20:9184-90. [PMID: 24954679 DOI: 10.1002/chem.201402827] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Muons, generated at a high-powered cyclotron, can capture electrons to form muonium atoms. Muon spin resonance spectra can be recorded for organosilyl radicals obtained by addition of muonium atoms to silylenes and silenes. We present a brief summary of progress in this new area since the first such experiments were reported in 2008.
Collapse
Affiliation(s)
- Robert West
- Organosilicon Research Center, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706 (USA), Fax: (+1) 608-262-1873.
| | | | | |
Collapse
|
41
|
Yamada K, Kawashima Y, Tachikawa M. Accurate Prediction of Hyperfine Coupling Constants in Muoniated and Hydrogenated Ethyl Radicals: Ab Initio Path Integral Simulation Study with Density Functional Theory Method. J Chem Theory Comput 2014; 10:2005-15. [PMID: 26580527 DOI: 10.1021/ct500027z] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We performed ab initio path integral molecular dynamics (PIMD) simulations with a density functional theory (DFT) method to accurately predict hyperfine coupling constants (HFCCs) in the ethyl radical (CβH3-CαH2) and its Mu-substituted (muoniated) compound (CβH2Mu-CαH2). The substitution of a Mu atom, an ultralight isotope of the H atom, with larger nuclear quantum effect is expected to strongly affect the nature of the ethyl radical. The static conventional DFT calculations of CβH3-CαH2 find that the elongation of one Cβ-H bond causes a change in the shape of potential energy curve along the rotational angle via the imbalance of attractive and repulsive interactions between the methyl and methylene groups. Investigation of the methyl-group behavior including the nuclear quantum and thermal effects shows that an unbalanced CβH2Mu group with the elongated Cβ-Mu bond rotates around the Cβ-Cα bond in a muoniated ethyl radical, quite differently from the CβH3 group with the three equivalent Cβ-H bonds in the ethyl radical. These rotations couple with other molecular motions such as the methylene-group rocking motion (inversion), leading to difficulties in reproducing the corresponding barrier heights. Our PIMD simulations successfully predict the barrier heights to be close to the experimental values and provide a significant improvement in muon and proton HFCCs given by the static conventional DFT method. Further investigation reveals that the Cβ-Mu/H stretching motion, methyl-group rotation, methylene-group rocking motion, and HFCC values deeply intertwine with each other. Because these motions are different between the radicals, a proper description of the structural fluctuations reflecting the nuclear quantum and thermal effects is vital to evaluate HFCC values in theory to be comparable to the experimental ones. Accordingly, a fundamental difference in HFCC between the radicals arises from their intrinsic molecular motions at a finite temperature, in particular the methyl-group behavior.
Collapse
Affiliation(s)
- Kenta Yamada
- Quantum Chemistry Division, Graduate School of Science, Graduate School of Nanobioscience, Yokohama City University , Yokohama 236-0027, Japan
| | - Yukio Kawashima
- RIKEN Advanced Institute for Computational Science , Minatojima-minami-machi 7-1-26, Chuo-ku, Kobe 650-0047, Japan
| | - Masanori Tachikawa
- Quantum Chemistry Division, Graduate School of Science, Graduate School of Nanobioscience, Yokohama City University , Yokohama 236-0027, Japan
| |
Collapse
|
42
|
Percival PW, Mozafari M, Brodovitch JC, Chandrasena L. Organic Free Radicals in Clathrate Hydrates Investigated by Muon Spin Spectroscopy. J Phys Chem A 2014; 118:1162-7. [DOI: 10.1021/jp411297s] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Paul W. Percival
- Department of Chemistry and
TRIUMF, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
| | - Mina Mozafari
- Department of Chemistry and
TRIUMF, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
| | - Jean-Claude Brodovitch
- Department of Chemistry and
TRIUMF, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
| | - Lalangi Chandrasena
- Department of Chemistry and
TRIUMF, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
| |
Collapse
|
43
|
McKenzie I, Salman Z, Giblin SR, Han YY, Leach GW, Morenzoni E, Prokscha T, Suter A. Polymer dynamics near the surface and in the bulk of poly(tetrafluoroethylene) probed by zero-field muon-spin-relaxation spectroscopy. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 89:022605. [PMID: 25353500 DOI: 10.1103/physreve.89.022605] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2013] [Indexed: 06/04/2023]
Abstract
The results of many experiments on polymers such as polystyrene indicate that the polymer chains near a free surface exhibit enhanced dynamics when compared with the bulk. We have investigated whether this is the case for poly(tetrafluoroethylene) (PTFE) by using zero-field muon-spin-relaxation spectroscopy to characterize a local probe, the F-Mu(+)-F state, which forms when spin-polarized positive muons are implanted in PTFE. Low-energy muons (implantation energies from 2.0 to 23.0 keV) were used to study the F-Mu(+)-F state between ∼ 23 and 191 nm from the free surface of PTFE. Measurements were also made with surface muons (4.1 MeV) where the mean implantation depth is on the order of ∼ 0.6 mm. The relaxation rate of the F-Mu(+)-F state up to ∼ 150 K was found to be significantly higher for muons implanted at 2.0 keV than for higher implantation energies, which suggests that the polymer chains in a region on the order of a few tens of nanometers from the free surface are more mobile than those in the bulk.
Collapse
Affiliation(s)
- Iain McKenzie
- Centre for Molecular and Materials Science, TRIUMF, Vancouver, British Columbia, Canada V6T 2A3 and Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6
| | - Zaher Salman
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - Sean R Giblin
- School of Physics and Astronomy, Cardiff University, Cardiff, CF24 3AA, United Kingdom
| | - Yun Yu Han
- Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6
| | - Gary W Leach
- Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6
| | - Elvezio Morenzoni
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - Thomas Prokscha
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - Andreas Suter
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| |
Collapse
|
44
|
McKenzie I. Muon spin spectroscopy of ferrocene: characterization of muoniated ferrocenyl radicals. Phys Chem Chem Phys 2014; 16:10600-6. [PMID: 24740122 DOI: 10.1039/c4cp00618f] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Iain McKenzie
- Centre for Molecular and Materials Science, TRIUMF, 4004 Wesbrook Mall, Vancouver, B.C., Canada.
| |
Collapse
|
45
|
McKenzie I, Scheuermann R, Cottrell SP, Lord JS, Tucker IM. Hyperfine coupling constants of the cyclohexadienyl radical in benzene and dilute aqueous solution. J Phys Chem B 2013; 117:13614-8. [PMID: 24144160 DOI: 10.1021/jp4068763] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The muon hyperfine coupling constant (Aμ) of the muoniated cyclohexadienyl radical (C6H6Mu) has been directly measured in a 5 mM solution of benzene in water by the radio-frequency muon spin resonance (RF-μSR) technique. The relative shift of Aμ in aqueous solution compared with the value in neat benzene (ΔAμ/Aμ = +0.98(5)% at 293 K) can now be compared directly with theoretical predictions. Application of the RF-μSR method to other dilute systems will provide extremely important information on understanding solvent effects.
Collapse
Affiliation(s)
- Iain McKenzie
- Centre for Molecular and Materials Science, TRIUMF , 4004 Wesbrook Mall, Vancouver, British Columbia V6T 2A3, Canada
| | | | | | | | | |
Collapse
|