1
|
Lombardi F, Ma J, Alexandropoulos DI, Komber H, Liu J, Myers WK, Feng X, Bogani L. Synthetic tuning of the quantum properties of open-shell radicaloids. Chem 2021. [DOI: 10.1016/j.chempr.2021.03.024] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
|
2
|
Lin CY, Ngendahimana T, Eaton GR, Eaton SS, Zadrozny JM. Counterion influence on dynamic spin properties in a V(iv) complex. Chem Sci 2019; 10:548-555. [PMID: 30746097 PMCID: PMC6335635 DOI: 10.1039/c8sc04122a] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2018] [Accepted: 10/17/2018] [Indexed: 12/18/2022] Open
Abstract
Using transition metal ions for spin-based applications, such as electron paramagnetic resonance imaging (EPRI) or quantum computation, requires a clear understanding of how local chemistry influences spin properties. Herein we report a series of four ionic complexes to provide the first systematic study of one aspect of local chemistry on the V(iv) spin - the counterion. To do so, the four complexes (Et3NH)2[V(C6H4O2)3] (1), (n-Bu3NH)2[V(C6H4O2)3] (2), (n-Hex3NH)2[V(C6H4O2)3] (3), and (n-Oct3NH)2[V(C6H4O2)3] (4) were probed by EPR spectroscopy in solid state and solution. Room temperature, solution X-band (ca. 9.8 GHz) continuous-wave electron paramagnetic resonance (CW-EPR) spectroscopy revealed an increasing linewidth with larger cations, likely a counterion-controlled tumbling in solution via ion pairing. In the solid state, variable-temperature (5-180 K) X-band (ca. 9.4 GHz) pulsed EPR studies of 1-4 in o-terphenyl glass demonstrated no effect on spin-lattice relaxation times (T 1), indicating little role for the counterion on this parameter. However, the phase memory time (T m) of 1 below 100 K is markedly smaller than those of 2-4. This result is counterintuitive, as 2-4 are relatively richer in 1H nuclear spin, hence, expected to have shorter T m. Thus, these data suggest an important role for counterion methyl groups on T m, and moreover provide the first instance of a lengthening T m with increasing nuclear spin quantity on a molecule.
Collapse
Affiliation(s)
- Chun-Yi Lin
- Department of Chemistry , Colorado State University , Fort Collins , Colorado 80523 , USA .
| | - Thacien Ngendahimana
- Department of Chemistry and Biochemistry , University of Denver , Denver , Colorado 80208 , USA . ;
| | - Gareth R Eaton
- Department of Chemistry and Biochemistry , University of Denver , Denver , Colorado 80208 , USA . ;
| | - Sandra S Eaton
- Department of Chemistry and Biochemistry , University of Denver , Denver , Colorado 80208 , USA . ;
| | - Joseph M Zadrozny
- Department of Chemistry , Colorado State University , Fort Collins , Colorado 80523 , USA .
| |
Collapse
|
3
|
Soetbeer J, Hülsmann M, Godt A, Polyhach Y, Jeschke G. Dynamical decoupling of nitroxides in o-terphenyl: a study of temperature, deuteration and concentration effects. Phys Chem Chem Phys 2018; 20:1615-1628. [DOI: 10.1039/c7cp07074h] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Distinct matrix- and molecule dependencies govern nitroxide decoherence in o-terphenyl at low temperatures, disclosing an optimal range for dynamical decoupling.
Collapse
Affiliation(s)
- Janne Soetbeer
- Laboratory of Physical Chemistry
- ETH Zürich
- CH-8093 Zürich
- Switzerland
| | - Miriam Hülsmann
- Bielefeld University
- Department of Chemistry
- D-33615 Bielefeld
- Germany
| | - Adelheid Godt
- Bielefeld University
- Department of Chemistry
- D-33615 Bielefeld
- Germany
| | - Yevhen Polyhach
- Laboratory of Physical Chemistry
- ETH Zürich
- CH-8093 Zürich
- Switzerland
| | - Gunnar Jeschke
- Laboratory of Physical Chemistry
- ETH Zürich
- CH-8093 Zürich
- Switzerland
| |
Collapse
|
4
|
Aalbergsjø SG, Sagstuen E. New Evidence for Hydroxyalkyl Radicals and Light- and Thermally Induced Trapped Electron Reactions in Rhamnose. Radiat Res 2015. [PMID: 26207688 DOI: 10.1667/rr14081.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Radical formation and trapping of radicals in X-irradiated crystals of rhamnose at 6 K were investigated using electron paramagnetic resonance (EPR), electron-nuclear double resonance (ENDOR) and ENDOR-induced EPR (EIE) techniques, complemented with periodic density functional theory (DFT) calculations. The two major radical species at 6 K were the O4-centered alkoxy radical and the intermolecularly trapped electron (IMTE), previously also detected by other authors. The current experimental results provided hyperfine coupling constants for these two species in good agreement with the previous data, thus providing a consistency check that improves their credibility. In addition to the O4-centered alkoxy radical and the IMTE, the C3-centered and C5-centered hydroxyalkyl radicals are the most prominent primary species at 6 K. The C3-centered radical appears in two slightly different conformations at 6 K, designated C and D. The C5-centered radical exhibits a coupling to a methyl group with tunneling rotation at 6 K, and analysis of one of the rotational substates (A) of the spin system yielded an understanding of the structure of this radical. Visible light bleaching of the IMTE at 6 K led to the C3-centered radical C, and thermal annealing above 6 K resulted in a conversion of the C to the D conformation. In addition, thermal annealing releases the IMTE, apparently resulting in the formation of the C2-centered radical. It is possible that the thermal decay of the IMTE also contributes to a small part of the C3-centered radical (D) population at 85 K. There are several other products trapped in rhamnose crystals directly after irradiation at 6 K, among which are resonance lines due to the C2 H-abstraction product. However, these other products are minority species and were not fully characterized in the current work.
Collapse
Affiliation(s)
| | - Einar Sagstuen
- Department of Physics, University of Oslo, N-0316, Oslo, Norway
| |
Collapse
|
5
|
Buscarino G, Alessi A, Agnello S, Boizot B, Gelardi FM, Boscaino R. Isolation of the CH3˙ rotor in a thermally stable inert matrix: first characterization of the gradual transition from classical to quantum behaviour at low temperatures. Phys Chem Chem Phys 2014; 16:13360-6. [DOI: 10.1039/c4cp01499e] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
By isolating the CH3˙ rotor in a stable clathrate host the gradual transition from classical to quantum behavior was observed.
Collapse
Affiliation(s)
- G. Buscarino
- Department of Physics and Chemistry
- University of Palermo
- I-90123 Palermo, Italy
| | - A. Alessi
- Department of Physics and Chemistry
- University of Palermo
- I-90123 Palermo, Italy
| | - S. Agnello
- Department of Physics and Chemistry
- University of Palermo
- I-90123 Palermo, Italy
| | - B. Boizot
- Laboratoire des Solides Irradiés
- Ecole Polytechnique
- Route de Saclay
- 91128 Palaiseau Cedex, France
| | - F. M. Gelardi
- Department of Physics and Chemistry
- University of Palermo
- I-90123 Palermo, Italy
| | - R. Boscaino
- Department of Physics and Chemistry
- University of Palermo
- I-90123 Palermo, Italy
| |
Collapse
|
6
|
Benetis NP, Dmitriev Y. Inertial rotation and matrix interaction effects on the EPR spectra of methyl radicals isolated in 'inert' cryogenic matrices. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:103201. [PMID: 21817418 DOI: 10.1088/0953-8984/21/10/103201] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The CW-EPR lineshapes of methyl and small methyl-like radicals trapped in noble gas matrices at liquid He temperatures are substantially different from the expected classical EPR spectra. At low temperatures they show small or negligible anisotropy in studies using different experimental techniques and have a temperature dependence that differs from systems whose motional dynamics is diffusion controlled. At liquid He temperatures, before the Boltzmann statistics take over in the classical high temperature realm, the spectral intensities are dominated by quantum statistics. These properties, which were obtained experimentally at temperatures about 5 K and lower, and up to about 20 K, can be attributed to quantum effects of inertial rotary motion and its coupling to the nuclear spin of the radical. Methyl-like radicals have nuclear-exchange symmetry and contain the lightest possible isotopes, protons, and deuterons. In the ideal case of absent radical-matrix interaction, the methyl rotation about the central heavier carbon atom guaranties minimal moments of inertia. However, the theoretical interpretation of the above effects and other related quantum effects, as well as recognition of the important physics which lead to them, is not a simple matter. The literature accumulated on the subject over the years is successful but contains several unresolved questions. Recently obtained spectra of methyl radicals in Kr, N(2) and CO matrices, which are less inert than the smaller noble gas Ar, were shown to exhibit greater, but certainly slight, overall anisotropic spectral features while in earlier experimental studies the anisotropy was practically absent. Even gases of smaller radii such as Ne and H(2) at liquid He temperatures show interesting differences as hosts of methyl radicals compared to Ar. Investigation of other possible causes of this difference, not excluding the experimentally controlled ones related to the sample preparation and the MW power saturation of the CW-EPR measurement, were conducted in this work.
Collapse
Affiliation(s)
- Nikolas P Benetis
- Nikolas-Ploutarch Benetis, Department of Pollution Control, Technological Educational Institution, TEI, West Macedonia, Kozani 501 00, Greece
| | | |
Collapse
|
7
|
Osmanoğlu Ş. Electron paramagnetic resonance of radiation damage of γ-irradiated diethylmalonic acid. J Mol Struct 2008. [DOI: 10.1016/j.molstruc.2007.07.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
|
8
|
Bowman MK, Mailer C, Halpern HJ. The solution conformation of triarylmethyl radicals. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2005; 172:254-267. [PMID: 15649753 DOI: 10.1016/j.jmr.2004.10.010] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2004] [Revised: 10/21/2004] [Indexed: 05/24/2023]
Abstract
Hyperfine coupling tensors to 1H, 2H, and natural abundance 13C were measured using X-band pulsed electron nuclear double resonance (ENDOR) spectroscopy for two triarylmethyl (trityl) radicals used in electron paramagnetic resonance imaging and oximetry: methyl tris(8-carboxy-2,2,6,6-tetramethyl-benzo[1,2d:4,5-d']bis(1,3)dithiol-4-yl) and methyl tris(8-carboxy-2,2,6,6-tetramethyl(-d3)-benzo[1,2d:4,5-d']bis(1,3)dithiol-4-yl). Quantum chemical calculations using density functional theory predict a structure that reproduces the experimentally determined hyperfine tensors. The radicals are propeller-shaped with the three aryl rings nearly mutually orthogonal. The central carbon atom carrying most of the unpaired electron spin density is surrounded by the sulfur atoms in the radical and is completely shielded from solvent. This structure explains features of the electron spin relaxation of these radicals and suggests ways in which the radicals can be chemically modified to improve their characteristics for imaging and oximetry.
Collapse
Affiliation(s)
- M K Bowman
- Structural Biology and Microimaging, Pacific Northwest National Laboratory, Richland, WA 99352-0999, USA.
| | | | | |
Collapse
|
9
|
Kim SH, Aznar C, Brynda M, Silks LA, Michalczyk R, Unkefer CJ, Woodruff WH, Britt RD. An EPR, ESEEM, Structural NMR, and DFT Study of a Synthetic Model for the Covalently Ring-Linked Tyrosine-Histidine Structure in the Heme-Copper Oxidases. J Am Chem Soc 2004; 126:2328-38. [PMID: 14982436 DOI: 10.1021/ja0303743] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report CW-EPR, ESEEM, and structural NMR results, as well as DFT calculations, on model compounds relevant to the unusual cross-linked Tyr-His (YH) moiety at the active site of the heme-copper oxidases. CW-EPR spectra of an (15)N isotopically labeled 4-methyl-2-(4-methyl-imidazole-1-yl)-phenol radical are nearly identical to those of the natural abundance (14)N compound. We obtain good simulations of these EPR spectra without including hyperfine couplings to the nitrogen nuclei. This implies that the electron distribution of the radical is largely localized on the phenol ring with only a small amount of spin delocalized onto the nitrogens of the imidazole. Using three-pulse ESEEM spectroscopy, we have successfully detected the two imidazole ring nitrogens, one near the "exact cancellation" ESEEM condition and the other more weakly coupled. We assign these to the imino and amino nitrogens, respectively, based on DFT calculations performed on this radical species. The experimental results and the supporting density functional calculations clearly show that the imidazole substituent has only a minor effect on the electronic structure of the substituted phenol radical.
Collapse
Affiliation(s)
- Sun Hee Kim
- Department of Chemistry, University of California, Davis, California 95616, USA
| | | | | | | | | | | | | | | |
Collapse
|
10
|
Shih S. A Generalized Unpaired Electron Spin Density Equation and Organic Hyperconjugation Mechanism. J CHIN CHEM SOC-TAIP 2003. [DOI: 10.1002/jccs.200300114] [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]
|
11
|
Yamada T, Komaguchi K, Shiotani M, Benetis NP, Sørnes AR. High-Resolution EPR and Quantum Effects on CH3, CH2D, CHD2, and CD3 Radicals under Argon Matrix Isolation Conditions. J Phys Chem A 1999. [DOI: 10.1021/jp984716g] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Tomoya Yamada
- Department of Applied Chemistry, Faculty of Engineering, Hiroshima University, Higashi-Hiroshima 739-8527, Japan, Department of Physics IFM, Chemical Physics, Linköping University, S-581 83 Linköping, Sweden, and Department of Physics, University of Oslo, P.O. Box 1048 Blindern, N-0316 Oslo, Norway
| | - Kenji Komaguchi
- Department of Applied Chemistry, Faculty of Engineering, Hiroshima University, Higashi-Hiroshima 739-8527, Japan, Department of Physics IFM, Chemical Physics, Linköping University, S-581 83 Linköping, Sweden, and Department of Physics, University of Oslo, P.O. Box 1048 Blindern, N-0316 Oslo, Norway
| | - Masaru Shiotani
- Department of Applied Chemistry, Faculty of Engineering, Hiroshima University, Higashi-Hiroshima 739-8527, Japan, Department of Physics IFM, Chemical Physics, Linköping University, S-581 83 Linköping, Sweden, and Department of Physics, University of Oslo, P.O. Box 1048 Blindern, N-0316 Oslo, Norway
| | - Nikolas P. Benetis
- Department of Applied Chemistry, Faculty of Engineering, Hiroshima University, Higashi-Hiroshima 739-8527, Japan, Department of Physics IFM, Chemical Physics, Linköping University, S-581 83 Linköping, Sweden, and Department of Physics, University of Oslo, P.O. Box 1048 Blindern, N-0316 Oslo, Norway
| | - Anders R. Sørnes
- Department of Applied Chemistry, Faculty of Engineering, Hiroshima University, Higashi-Hiroshima 739-8527, Japan, Department of Physics IFM, Chemical Physics, Linköping University, S-581 83 Linköping, Sweden, and Department of Physics, University of Oslo, P.O. Box 1048 Blindern, N-0316 Oslo, Norway
| |
Collapse
|