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Mardini M, Palani RS, Ahmad IM, Mandal S, Jawla SK, Bryerton E, Temkin RJ, Sigurdsson ST, Griffin RG. Frequency-swept dynamic nuclear polarization. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2023; 353:107511. [PMID: 37385067 DOI: 10.1016/j.jmr.2023.107511] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Revised: 06/14/2023] [Accepted: 06/15/2023] [Indexed: 07/01/2023]
Abstract
Dynamic nuclear polarization (DNP) improves the sensitivity of NMR spectroscopy by the transfer of electron polarization to nuclei via irradiation of electron-nuclear transitions with microwaves at the appropriate frequency. For fields > 5 T and using g ∼ 2 electrons as polarizing agents, this requires the availability of microwave sources operating at >140 GHz. Therefore, microwave sources for DNP have generally been continuous-wave (CW) gyrotrons, and more recently solid state, oscillators operating at a fixed frequency and power. This constraint has limited the DNP mechanisms which can be exploited, and stymied the development of new time domain mechanisms. We report here the incorporation of a microwave source enabling facile modulation of frequency, amplitude, and phase at 9 T (250 GHz microwave frequency), and we have used the source for magic-angle spinning (MAS) NMR experiments. The experiments include investigations of CW DNP mechanisms, the advantage of frequency-chirped irradiation, and a demonstration of an Overhauser enhancement of ∼25 with a recently reported water-soluble BDPA radical, highlighting the potential for affordable and compact microwave sources to achieve significant enhancement in aqueous samples, including biological macromolecules. With the development of suitable microwave amplifiers, it should permit exploration of multiple new avenues involving time domain experiments.
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Affiliation(s)
- Michael Mardini
- Department of Chemistry and Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
| | - Ravi Shankar Palani
- Department of Chemistry and Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
| | - Iram M Ahmad
- Department of Chemistry, Science Institute, University of Iceland, Reykjavik, Iceland
| | - Sucharita Mandal
- Department of Chemistry, Science Institute, University of Iceland, Reykjavik, Iceland
| | - Sudheer K Jawla
- Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
| | - Eric Bryerton
- Virginia Diodes Corporation, Charlottesville, VA 22902, United States
| | - Richard J Temkin
- Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
| | - Snorri Th Sigurdsson
- Department of Chemistry, Science Institute, University of Iceland, Reykjavik, Iceland
| | - Robert G Griffin
- Department of Chemistry and Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, United States.
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2
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Avalos CE, Richert S, Socie E, Karthikeyan G, Casano G, Stevanato G, Kubicki DJ, Moser JE, Timmel CR, Lelli M, Rossini AJ, Ouari O, Emsley L. Enhanced Intersystem Crossing and Transient Electron Spin Polarization in a Photoexcited Pentacene–Trityl Radical. J Phys Chem A 2020; 124:6068-6075. [DOI: 10.1021/acs.jpca.0c03498] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Claudia E. Avalos
- Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Sabine Richert
- Centre for Advanced Electron Spin Resonance (CAESR), University of Oxford, South Parks Road, OX1 3QR Oxford, United Kingdom
| | - Etienne Socie
- Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | | | | | - Gabriele Stevanato
- Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Dominik J. Kubicki
- Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Jacques E. Moser
- Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Christiane R. Timmel
- Centre for Advanced Electron Spin Resonance (CAESR), University of Oxford, South Parks Road, OX1 3QR Oxford, United Kingdom
| | - Moreno Lelli
- Center of Magnetic Resonance (CERM), University of Florence, Via Luigi Sacconi 6, 50019 Sesto Fiorentino, Italy
- Department of Chemistry “Ugo Schiff”, University of Florence, Via della Lastruccia 3, 50019 Sesto Fiorentino, Italy
| | - Aaron J. Rossini
- Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | | | - Lyndon Emsley
- Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
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3
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Mandal S, Sigurdsson ST. On the Limited Stability of BDPA Radicals. Chemistry 2020; 26:7486-7491. [PMID: 32396245 DOI: 10.1002/chem.202001084] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2020] [Indexed: 11/08/2022]
Abstract
1,3-Bis(diphenylene)-2-phenylallyl (BDPA)-based radicals are of interest as polarizing agents for dynamic nuclear polarization (DNP). For this purpose, a BDPA-nitroxide biradical, employing a phosphodiester linkage, was synthesized. Contrary to what is commonly assumed, BDPA-derived radicals were observed to have limited stability. Hence, the effects of various factors on the stability of BDPA radicals were investigated. Solvent polarity was found to play a significant role on degradation; a polar BDPA radical was observed to degrade faster in a non-polar solvent, whereas non-polar radicals were more unstable in polar solvents. The rate of decomposition was found to increase non-linearly with increasing radical concentration; a 2-fold increase in concentration led to a 3-fold increase in the rate of degradation. Collectively, these results indicate that the dimerization is a significant degradation pathway for BDPA radicals and indeed, a dimer of one BDPA radical was detected by mass spectrometry.
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Affiliation(s)
- Sucharita Mandal
- Department of Chemistry, Science Institute, University of Iceland, Dunhaga 3, 107, Reykjavik, Iceland
| | - Snorri Th Sigurdsson
- Department of Chemistry, Science Institute, University of Iceland, Dunhaga 3, 107, Reykjavik, Iceland
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4
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Wilson CB, Edwards DT, Clayton JA, Han S, Sherwin MS. Dressed Rabi Oscillation in a Crystalline Organic Radical. PHYSICAL REVIEW LETTERS 2020; 124:047201. [PMID: 32058731 DOI: 10.1103/physrevlett.124.047201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Revised: 10/04/2019] [Indexed: 06/10/2023]
Abstract
Free electron laser-powered pulsed electron paramagnetic resonance experiments performed at 240 GHz/8.56 T on the crystalline organic radical 1,3-bisdiphenylene-2-phenylallyl reveal a tip-angle dependent resonant frequency. Frequency shifts as large as 11 MHz (45 ppm) are observed during a single Rabi oscillation. We attribute the frequency shifts to a "dressing" of the nutation by spin-spin interactions. A nonlinear semiclassical model which includes a temperature- and sample-geometry-dependent demagnetizing field reproduces experimental results. Because experiments are performed without a cavity, radiation damping, the most common nonlinear interaction in magnetic resonance, is negligible in our experiments.
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Affiliation(s)
- C Blake Wilson
- Department of Physics, University of California, Santa Barbara, Santa Barbara, California, USA
- Institute for Terahertz Science and Technology, University of California, Santa Barbara, Santa Barbara, California, USA
| | - Devin T Edwards
- Department of Physics, University of California, Santa Barbara, Santa Barbara, California, USA
- Institute for Terahertz Science and Technology, University of California, Santa Barbara, Santa Barbara, California, USA
| | - Jessica A Clayton
- Department of Physics, University of California, Santa Barbara, Santa Barbara, California, USA
- Institute for Terahertz Science and Technology, University of California, Santa Barbara, Santa Barbara, California, USA
| | - Songi Han
- Institute for Terahertz Science and Technology, University of California, Santa Barbara, Santa Barbara, California, USA
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California, USA
| | - Mark S Sherwin
- Department of Physics, University of California, Santa Barbara, Santa Barbara, California, USA
- Institute for Terahertz Science and Technology, University of California, Santa Barbara, Santa Barbara, California, USA
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5
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Mandal S, Sigurdsson ST. Water-soluble BDPA radicals with improved persistence. Chem Commun (Camb) 2020; 56:13121-13124. [DOI: 10.1039/d0cc04920d] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
1,3-Bis(diphenylene)-2-phenylallyl (BDPA) radicals are promising polarizing agents for dynamic nuclear polarization (DNP) NMR spectroscopy. BDPAs containing tetraalkyl/aryl-ammonium groups have increased persistence and solubility in polar solvents.
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Affiliation(s)
- Sucharita Mandal
- University of Iceland
- Department of Chemistry
- Science Institute
- Reykjavik 107
- Iceland
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6
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Wang P, Lin S, Lin Z, Peeks MD, Van Voorhis T, Swager TM. A Semiconducting Conjugated Radical Polymer: Ambipolar Redox Activity and Faraday Effect. J Am Chem Soc 2018; 140:10881-10889. [DOI: 10.1021/jacs.8b06193] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Affiliation(s)
- Pan Wang
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
- Institute for Soldier Nanotechnologies, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Sibo Lin
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Zhou Lin
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Martin D. Peeks
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
- Institute for Soldier Nanotechnologies, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Troy Van Voorhis
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Timothy M. Swager
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
- Institute for Soldier Nanotechnologies, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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Bodzioch A, Zheng M, Kaszyński P, Utecht G. Functional group transformations in derivatives of 1,4-dihydrobenzo[1,2,4]triazinyl radical. J Org Chem 2014; 79:7294-310. [PMID: 25068765 DOI: 10.1021/jo500898e] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Transformations of functional groups OCOPh, OCH2Ph, I, NO2, and CO2Me in Blatter's radical derivatives 1-5 were investigated in order to develop synthetic tools for incorporation of the benzo[1,2,4]triazinyl system into complex molecular architectures. Thus, basic hydrolysis of OCOPh or Pd-catalyzed debenzylation of OCH2Ph gave phenol functionality, which was acylated and alkylated. Pd-catalyzed Suzuki, Negishi, Sonogashira, and Heck C-C cross-coupling reactions of iodo derivatives 1c, 1d, and 2d were also successful and efficient. Reduction of NO2 in 1e led to aniline derivative 1t, which was reductively alkylated with hexanal and coupled to l-proline. Selected benzo[1,2,4]triazinyl radicals were characterized by EPR and electronic absorption spectroscopy, and the results were analyzed in tandem with DFT computational methods. Lastly, the mechanism for formation of the 1,4-dihydrobenzo[1,2,4]triazine ring was investigated using the B3LYP/6-31G(2d,p) method.
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Affiliation(s)
- Agnieszka Bodzioch
- Organic Materials Research Group Department of Chemistry, Vanderbilt University , Nashville, Tennessee 37235, United States
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Haze O, Corzilius B, Smith AA, Griffin RG, Swager TM. Water-soluble narrow-line radicals for dynamic nuclear polarization. J Am Chem Soc 2012; 134:14287-90. [PMID: 22917088 DOI: 10.1021/ja304918g] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The synthesis of air-stable, highly water-soluble organic radicals containing a 1,3-bis(diphenylene)-2-phenylallyl (BDPA) core is reported. A sulfonated derivative, SA-BDPA, retains the narrow electron paramagnetic resonance linewidth (<30 MHz at 5 T) of the parent BDPA in highly concentrated glycerol/water solutions (40 mM), which enables its use as polarizing agent for solid effect dynamic nuclear polarization (SE DNP). A sensitivity enhancement of 110 was obtained in high-field magic-angle-spinning (MAS) NMR experiments. The ease of synthesis and high maximum enhancements obtained with the BDPA-based radicals constitute a major advance over the trityl-type narrow-line polarization agents.
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Affiliation(s)
- Olesya Haze
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
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9
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Hu KN. Polarizing agents and mechanisms for high-field dynamic nuclear polarization of frozen dielectric solids. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2011; 40:31-41. [PMID: 21855299 PMCID: PMC3171565 DOI: 10.1016/j.ssnmr.2011.08.001] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2011] [Revised: 08/01/2011] [Accepted: 08/01/2011] [Indexed: 05/05/2023]
Abstract
This article provides an overview of polarizing mechanisms involved in high-frequency dynamic nuclear polarization (DNP) of frozen biological samples at temperatures maintained using liquid nitrogen, compatible with contemporary magic-angle spinning (MAS) nuclear magnetic resonance (NMR). Typical DNP experiments require unpaired electrons that are usually exogenous in samples via paramagnetic doping with polarizing agents. Thus, the resulting nuclear polarization mechanism depends on the electron and nuclear spin interactions induced by the paramagnetic species. The Overhauser Effect (OE) DNP, which relies on time-dependent spin-spin interactions, is excluded from our discussion due the lack of conducting electrons in frozen aqueous solutions containing biological entities. DNP of particular interest to us relies primarily on time-independent, spin-spin interactions for significant electron-nucleus polarization transfer through mechanisms such as the Solid Effect (SE), the Cross Effect (CE) or Thermal Mixing (TM), involving one, two or multiple electron spins, respectively. Derived from monomeric radicals initially used in high-field DNP experiments, bi- or multiple-radical polarizing agents facilitate CE/TM to generate significant NMR signal enhancements in dielectric solids at low temperatures (<100 K). For example, large DNP enhancements (∼300 times at 5 T) from a biologically compatible biradical, 1-(TEMPO-4-oxy)-3-(TEMPO-4-amino)propan-2-ol (TOTAPOL), have enabled high-resolution MAS NMR in sample systems existing in submicron domains or embedded in larger biomolecular complexes. The scope of this review is focused on recently developed DNP polarizing agents for high-field applications and leads up to future developments per the CE DNP mechanism. Because DNP experiments are feasible with a solid-state microwave source when performed at <20K, nuclear polarization using lower microwave power (<100 mW) is possible by forcing a high proportion of biradicals to fulfill the frequency matching condition of CE (two EPR frequencies separated by the NMR frequency) using the strategies involving hetero-radical moieties and/or molecular alignment. In addition, the combination of an excited triplet and a stable radical might provide alternative DNP mechanisms without the microwave requirement.
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Affiliation(s)
- Kan-Nian Hu
- Laboratory of Chemical Physics, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
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10
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Lumata L, Ratnakar SJ, Jindal A, Merritt M, Comment A, Malloy C, Sherry AD, Kovacs Z. BDPA: an efficient polarizing agent for fast dissolution dynamic nuclear polarization NMR spectroscopy. Chemistry 2011; 17:10825-7. [PMID: 21919088 DOI: 10.1002/chem.201102037] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2011] [Indexed: 11/06/2022]
Affiliation(s)
- Lloyd Lumata
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas 75390-8568, USA
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11
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Mitchell DG, Quine RW, Tseitlin M, Weber RT, Meyer V, Avery A, Eaton SS, Eaton GR. Electron Spin Relaxation and Heterogeneity of the 1:1 α,γ-Bisdiphenylene-β-phenylallyl (BDPA)/Benzene Complex. J Phys Chem B 2011; 115:7986-90. [DOI: 10.1021/jp201978w] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Deborah G. Mitchell
- Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado 80208, United States
| | - Richard W. Quine
- School of Engineering and Computer Science, University of Denver, Denver, Colorado 80208, United States
| | - Mark Tseitlin
- Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado 80208, United States
| | - Ralph T. Weber
- Bruker BioSpin, Billerica, Massachusetts 01821, United States
| | - Virginia Meyer
- Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado 80208, United States
| | - Azure Avery
- Department of Physics and Astronomy, University of Denver, Denver, Colorado 80208, United States
| | - Sandra S. Eaton
- Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado 80208, United States
| | - Gareth R. Eaton
- Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado 80208, United States
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12
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Dane EL, Swager TM. Carbanionic Route to Electroactive Carbon-Centered Anion and Radical Oligomers. Org Lett 2010; 12:4324-7. [DOI: 10.1021/ol1017728] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Eric L. Dane
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139
| | - Timothy M. Swager
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139
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