Applied Magnetic Resonance最新文献

{"title":"Adiabatic Spin Dynamics by Chirped Microwave Pulses Based on AWG-ESR","authors":"Kazunobu Sato,&nbsp;Rei Hirao,&nbsp;Satoru Yamamoto,&nbsp;Konstantin L. Ivanov,&nbsp;Takeji Takui","doi":"10.1007/s00723-022-01513-8","DOIUrl":"10.1007/s00723-022-01513-8","url":null,"abstract":"<div><p>We present methods for optimizing frequency sweeps for “fast” adiabatic inversion in ESR spectroscopy. To perform the sought optimization, we need to either exploit “constant adiabaticity” chirps or utilize the gradient ascent pulse engineering (GRAPE) method: in these ways, the Δ(<i>t</i>) profiles are evaluated, which allow one to minimize the duration of the chirps. Arbitrary waveform generator-based ESR (AWG-ESR) enables us to apply versatile MW-shaped pulses and to control dynamics of the spin systems under study. Spin dynamics for spin inversion by the shaped pulses were observed. Comparison of different frequency sweeps applied to both a homogeneous ESR signal and a spin packet of inhomogeneously broadened ESR signals indicates that the duration of the adiabatic sweeps can be significantly reduced.\u0000</p></div>","PeriodicalId":469,"journal":{"name":"Applied Magnetic Resonance","volume":"54 1","pages":"183 - 201"},"PeriodicalIF":1.0,"publicationDate":"2022-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4115569","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Electron Spin Relaxation Rates of Radicals in Irradiated Boron Oxides","authors":"Thacien Ngendahimana,&nbsp;Whylder Moore,&nbsp;Autumn Canny,&nbsp;Sandra S. Eaton,&nbsp;Gareth R. Eaton","doi":"10.1007/s00723-022-01514-7","DOIUrl":"10.1007/s00723-022-01514-7","url":null,"abstract":"<div><p>The boron–oxygen hole center (BOHC) that is formed by irradiation of boron oxides has previously been characterized extensively by continuous wave and pulsed electron paramagnetic resonance. We now report that the electron spin relaxation rates for the BOHC in irradiated high purity B₂O₃, practical grade B₂O₃, and sodium tetraborate Na₂B₄O₇ exhibit substantial sample dependence. Because of the low magnetic moments for the boron nuclei, the spin echo dephasing is dominated by electron–electron interaction (<i>T</i>₂) instead of the nuclear spin diffusion that dominates dephasing for organic radicals in lattices with high proton concentrations. The higher local concentration of defects in a sample of practical grade B₂O₃ than in a sample of reagent grade B₂O₃, shortens <i>T</i>_m (spin echo dephasing) and causes extensive cross relaxation contributions to <i>T</i>₁ (spin lattice relaxation) at 10 K. At temperatures below about 60 K <i>T</i>₁ is shorter for the BOHC in B₂O₃ than in sodium tetraborate or for the radical formed by irradiation of calcium metaborate. <i>T</i>₁ for the BOHC and the radical in irradiated calcium metaborate are shorter than for other irradiated solids including glycylglycine, <span>l</span>-alanine and the E´ center in quartz. The temperature dependence of <i>T</i>₁ for the BOHC in B₂O₃ is dominated by the Raman process with a lower Debye temperature than for the radical formed by irradiation of calcium metaborate.</p></div>","PeriodicalId":469,"journal":{"name":"Applied Magnetic Resonance","volume":"54 3","pages":"359 - 370"},"PeriodicalIF":1.0,"publicationDate":"2022-11-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5502950","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Anisotropic g-Tensor and Abragam’s Dipole Alphabet: New Words","authors":"Alexander G. Maryasov,&nbsp;Michael K. Bowman","doi":"10.1007/s00723-022-01512-9","DOIUrl":"10.1007/s00723-022-01512-9","url":null,"abstract":"<div><p>The impact of g-tensor anisotropy on the dipole–dipole interaction (DDI) of Kramers paramagnetic centers (PCs) with spins of ½ is theoretically considered in the point dipole limit. The magnetic moment may be expressed in terms of the tensor <i>G</i> = <i>g</i>^<i>T</i>.<i>g</i> and the signature of the g-tensor (sign of its determinant). This means that the DDI spin Hamiltonian depends only on the G of the PCs involved and on their respective <i>g</i>-tensor signatures. Abragam’s dipole alphabet for isotropic PCs consists of six letters by Abragam (The principles of nuclear magnetism, Clarendon Press, Oxford, 1961), each letter a product of a spin operator and a spatial coordinate. Pairs of letters correspond to zero-, single-, and double-quantum coherences. In the case of like anisotropic spins, the dipole alphabet has the same structure but with different coordinate factors that depend on the tensor G and its orientation in the laboratory frame. In the general case, anisotropic spins have nine letters in their dipole alphabet. Analytic expressions for all the letters are obtained. The DDI spin Hamiltonian for anisotropic PCs can contain terms having the appearance of isotropic exchange-like and quadrupolar-like interactions resulting entirely from the DDI.</p></div>","PeriodicalId":469,"journal":{"name":"Applied Magnetic Resonance","volume":"54 1","pages":"29 - 45"},"PeriodicalIF":1.0,"publicationDate":"2022-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00723-022-01512-9.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4907511","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"pH of Water Intercalated into Graphite Oxide as Determined by EPR Spectroscopy","authors":"Tatiana S. Yankova,&nbsp;Natalia A. Chumakova","doi":"10.1007/s00723-022-01509-4","DOIUrl":"10.1007/s00723-022-01509-4","url":null,"abstract":"<div><p>Two pH-sensitive spin probes 4-(methylamino)-2-ethyl-5,5-dimethyl-4-pyridine-2-yl-2,5-dihydro-1<i>H</i>-imidazol-1-oxyl (DPI, also known as MEP) and 2,2,3,5,5-pentamethyl-2,5-dihydro-1<i>H</i>-imidazol-1-oxyl (MTI) were used to measure pH of water intercalated in Brodie graphite oxide. The pH value was found to be 2.25 ± 0.05 immediately after adding water to graphite oxide and decreased to 1.75 ± 0.05 during ca<i>.</i> 30 h.</p></div>","PeriodicalId":469,"journal":{"name":"Applied Magnetic Resonance","volume":"54 2","pages":"311 - 320"},"PeriodicalIF":1.0,"publicationDate":"2022-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4840921","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Möbius-Strip Topology of Expanded Porphyrins: A Minireview on EPR, ENDOR and DFT MO Studies","authors":"Klaus Möbius,&nbsp;Martin Plato,&nbsp;Anton Savitsky","doi":"10.1007/s00723-022-01507-6","DOIUrl":"10.1007/s00723-022-01507-6","url":null,"abstract":"<div><p>The one-sided Möbius strip with its characteristic 180° twist in the loop has inspired philosophers, artists and scientists since hundreds of years and continues to do so. On the molecular level, only in the last 15 years have some groups succeeded in synthesizing new expanded porphyrin compounds large enough to adopt Möbius-strip topology and Möbius aromaticity, the first being Lechosław Latos-Grażyński and collaborators in Wroclaw (2007) and Atsuhiro Osuka and collaborators in Kyoto (2008). We report on new studies of expanded porphyrins with either Möbius topology or Hückel topology that were synthesized in these laboratories. In this minireview, we focus on recent continuous-wave and time-resolved EPR, ENDOR and DFT MO studies on open-shell states of di-<i>p</i>-benzi[28]hexaphyrin(1.1.1.1.1.1), specifically, on the ground-state radical cation doublet state (total electron spin <i>S</i> = 1/2) and the first excited triplet state (<i>S</i> = 1). The review is largely based on the results and discussions of two previous publications: Möbius et al. (Appl Magn Reson 47:757–780, 2016) and Ema et al. (J Phys Chem Lett 9:2685–2690, 2018). In the open-shell systems, besides the electron-nuclear hyperfine couplings also the zero-field interaction tensor turned out to be a viable sensor for electronic structure changes between Möbius and Hückel topologies. In the Outlook section, we address the cyclotides, a new class of natural circular mini-proteins, usually less than 100 amino acids long. They are distinguished by exceptional chemical and biological stability. This is due to topological constraints imposed by <i>threefoil</i> knot and Möbius-strip formation. As a result, their physical qualities are “topologically protected”. This makes them highly interesting for medical or agricultural applications, for example as novel active ingredients against autoimmune diseases, viral infections, or as agents against insect damage to crops.</p></div>","PeriodicalId":469,"journal":{"name":"Applied Magnetic Resonance","volume":"54 1","pages":"7 - 28"},"PeriodicalIF":1.0,"publicationDate":"2022-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00723-022-01507-6.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4314816","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Magnetic Properties of La0.81Sr0.19Mn0.9Fe0.1−xZnxO3 (x = 0, x = 0.05)","authors":"R. M. Eremina,&nbsp;I. V. Yatsyk,&nbsp;Z. Y. Seidov,&nbsp;F. G. Vagizov,&nbsp;V. A. Shustov,&nbsp;A. G. Badelin,&nbsp;V. K. Karpasyuk,&nbsp;D. S. Abdinov,&nbsp;M. M. Tagiev,&nbsp;S. Kh. Estemirova,&nbsp;H.-A. Krug von Nidda","doi":"10.1007/s00723-022-01510-x","DOIUrl":"10.1007/s00723-022-01510-x","url":null,"abstract":"<div><p>Magnetic properties of polycrystalline La_0.81Sr_0.19Mn_0.9Fe_{0.1−<i>x</i>}Zn_<i>x</i>O₃ (<i>x</i> = 0, 0<i>.</i>05) have been investigated by means of electron spin resonance, magnetic susceptibility, and Mössbauer measurements. Both samples show a clear ferromagnetic transition. The Curie temperature <i>T</i>_C decreases on increasing Fe content (<i>x</i> = 0.05—<i>T</i>_C = 222 K; <i>x</i> = 0—<i>T</i>_C = 148 K). Mössbauer studies indicate that Fe in these compounds is in the trivalent high-spin state. The temperature evolution of the Mössbauer spectra at low temperatures (<i>T</i> &lt; <i>T</i>_C) is typical for ferromagnetic clusters with a wide distribution in size and magnetic correlation length. The inverse susceptibility of all the samples deviates from the Curie–Weiss law above <i>T</i>_C, indicating the presence of fluctuations on approaching magnetic order. An anomalous downturn of the inverse susceptibility for <i>x</i> = 0<i>.</i>05 significantly above <i>T</i>_C and the concomitant observation of ferromagnetic resonance signals coexisting with the paramagnetic resonance up to approximately room temperature, is caused by a Griffiths-like behavior. This regime is characterized by the coexistence of ferromagnetic entities within the globally paramagnetic phase.</p></div>","PeriodicalId":469,"journal":{"name":"Applied Magnetic Resonance","volume":"54 4-5","pages":"449 - 461"},"PeriodicalIF":1.0,"publicationDate":"2022-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00723-022-01510-x.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4316720","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Coupling Sub-nanoliter BDPA Organic Radical Spin Ensembles with YBCO Inverse Anapole Resonators","authors":"Claudio Bonizzoni,&nbsp;Maksut Maksutoglu,&nbsp;Alberto Ghirri,&nbsp;Johan van Tol,&nbsp;Bulat Rameev,&nbsp;Marco Affronte","doi":"10.1007/s00723-022-01505-8","DOIUrl":"10.1007/s00723-022-01505-8","url":null,"abstract":"<div><p>We report the development and test of planar microwave Inverse Anapole Resonators (IARs) made of superconducting Yttrium Barium Copper Oxide (YBCO) for electron spin resonance spectroscopy on small samples. We first characterize our resonators in zero field and then by carrying out transmission spectroscopy on a diluted <span>(alpha ,gamma )</span>-bisdiphenylene-<span>(beta )</span>-phenylally (BDPA) organic radical spin ensemble in an applied magnetic field. These IARs allow us to carry out electron spin resonance spectroscopy both in continuous-wave and pulsed-wave mode, and to estimate the spin memory time of BDPA. The comparison with the results obtained for the same sample on typical linear coplanar resonators shows an improvement by <span>(approx 2text { - up to},3)</span> – orders of magnitude in spin sensitivity, with effective sensing volumes below 1 nanoliter. The best sensitivity we achieved is <span>(Sapprox ,10^{7},text {spin}/sqrt{mathrm{Hz}})</span> in the pulsed-wave regime. These results compare well with similar experiments reported in the literature.</p></div>","PeriodicalId":469,"journal":{"name":"Applied Magnetic Resonance","volume":"54 1","pages":"143 - 164"},"PeriodicalIF":1.0,"publicationDate":"2022-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4100152","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Magnetic-Field Dependence of LC-Photo-CIDNP in the Presence of Target Molecules Carrying a Quasi-Isolated Spin Pair","authors":"Siyu Li,&nbsp;Hanming Yang,&nbsp;Heike Hofstetter,&nbsp;Marco Tonelli,&nbsp;Silvia Cavagnero","doi":"10.1007/s00723-022-01506-7","DOIUrl":"10.1007/s00723-022-01506-7","url":null,"abstract":"<div><p>NMR spectroscopy is well known for its high atomic-scale resolution, especially at high applied magnetic field. However, the sensitivity of this technique is marginal. Liquid-state low-concentration photo-chemically induced dynamic nuclear polarization (LC-photo-CIDNP) is a promising emerging technology capable of enhancing NMR sensitivity in solution. LC-photo-CIDNP works well on solvent-exposed Trp and Tyr residues, either in isolation or within proteins. This study explores the magnetic-field dependence of the LC-photo-CIDNP experienced by two tryptophan isotopologs in solution upon in situ LED-mediated optical irradiation. Out of the two uniformly ¹³C,¹⁵N-labeled Trp (Trp-U-¹³C,¹⁵N) and Trp-α-¹³C-β,β,2,4,5,6,7-d₇ species employed here, only the latter bears a quasi-isolated ¹H^α-¹³C^α spin pair. Computer simulations of the predicted polarization due to geminate recombination of both species display a roughly bell-shaped field dependence. Specifically, Trp-U-¹³C,¹⁵N is predicted to show a fairly weak field dependence with a maximum polarization at ca. 500 MHz (11.7 T). In contrast, Trp-α-¹³C-β,β,2,4,5,6,7-d₇ is expected to show a much sharper field dependence with a polarization maximum at ca. 200 MHz (4.7 T). Experimental LC-photo-CIDNP studies on both Trp isotopologs (1 μM concentration) are consistent with the theoretical predictions. In summary, this study highlights the prominent field-dependence of LC-photo-CIDNP enhancements (ε) experienced by Trp isotopologs bearing a quasi-isolated spin pair.</p></div>","PeriodicalId":469,"journal":{"name":"Applied Magnetic Resonance","volume":"54 1","pages":"59 - 75"},"PeriodicalIF":1.0,"publicationDate":"2022-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00723-022-01506-7.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4632005","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Regioisomers of 2,5,6,7,8-Pentaaryl-1H-Azepino[3,2,1-ij]Quinazoline-1,3(2H)-Dione Containing Various Aryl Substituents in the Azepine Ring: Structure Determination Using NMR Methods","authors":"Julia A. Pronina,&nbsp;Darya D. Komolova,&nbsp;Vitali M. Boitsov,&nbsp;Alexander V. Stepakov,&nbsp;Stanislav I. Selivanov","doi":"10.1007/s00723-022-01496-6","DOIUrl":"10.1007/s00723-022-01496-6","url":null,"abstract":"<div><p>NMR spectroscopy methods were used to prove the structures of two similar regioisomers of 2,5,6,7,8-pentaaryl-1<i>H</i>-azepino[3,2,1-<i>ij</i>]quinazoline-1,3(2<i>H</i>)-dione containing various aryl substituents in the azepine ring which were obtained as reaction products and existed in CDCl₃ as inseparable mixture of two compounds with almost equal (56:44) relation between them. Complete signal assignment in ¹H and ¹³C spectra of each compound was made by using some homo- and heteronuclear NMR experiments. Long-range distance estimation (up to 5.0 Å) on the base of nuclear Overhauser enhancement approach (NOE) at conditions of extreme-narrow limits (ω_oτ_c &lt;  &lt; 1) was used to determine the quantitative level the internuclear distances between protons H6 and H8 situated in the rigid part of molecules and the nearest <i>ortho</i>- and <i>meta</i>-protons in mobile phenyl rings Ph⁵ and Ph², respectively. The distance difference between the calculated and experimental values in all cases was not more than 10%. These results allowed us to prove that a dominant regioisomer (<b>3a</b>) has <i>para</i>-methoxy-substituted rings at positions <b>9</b> and <b>12</b> of seven-membered ring C, and a minor regioisomer (<b>3d</b>) has these rings at positions <b>10</b> and <b>12</b>. The results of an independent approach based on the comparison of the chemical shifts of the ¹H and ¹³C nuclei of the regioisomers under study are in full agreement (or do not contradict) with the obtained conclusions based on the quantitative NOE measurements of interproton distances. The methodological approach on the basis of long-range distance estimation by NOE tested in this work can be used to establish the structure of inseparable mixtures of two or more compounds or to solve similar problems under conditions of complex mixtures of closely related organic compounds.</p></div>","PeriodicalId":469,"journal":{"name":"Applied Magnetic Resonance","volume":"53 12","pages":"1677 - 1691"},"PeriodicalIF":1.0,"publicationDate":"2022-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00723-022-01496-6.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4515588","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Analysis of 2D Maps Based on Similarity in DFT-Calculated vs Experimental 13C–15N Spin Couplings for a Representative Sample of Conformationally Rigid and Structurally Fixed Nitrogen-Containing Organic Compounds","authors":"Vladislav V. Stanishevskiy,&nbsp;Alla K. Shestakova,&nbsp;Vyacheslav A. Chertkov","doi":"10.1007/s00723-022-01503-w","DOIUrl":"10.1007/s00723-022-01503-w","url":null,"abstract":"<div><p>In this work, we carried out an extended verification of the ¹³C–¹⁵N spin–spin coupling constants as a new structural indicator of nitrogen-containing organic compounds. In this regard, we performed a quantum-chemical calculation (B3LYP with basis set 6-311++G(2<i>df</i>,2<i>p</i>)) for a representative sample of 193 spin–spin couplings for the currently known literature experimental data on them in the conformationally rigid and structurally fixed compounds. Comparison of theoretical couplings with experimental ones shows a statistically significant good to excellent agreement. A parallel analysis of the variability of the calculated values of ¹³C–¹⁵N spin bonds with the variability of experimental data within groups of related compounds turned out to be practically useful. The approach developed can be used to quite reasonably determine the signs of spin–spin coupling constants ¹³C–¹⁵N. It can also provide important additional information for assigning ¹³C peaks in cases where this cannot be done using standard NMR spectroscopy techniques.</p></div>","PeriodicalId":469,"journal":{"name":"Applied Magnetic Resonance","volume":"53 12","pages":"1693 - 1713"},"PeriodicalIF":1.0,"publicationDate":"2022-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00723-022-01503-w.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4477093","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}