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J Seliger - One of the best experts on this subject based on the ideXlab platform.
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Nuclear Quadrupole Resonance nqr a useful spectroscopic tool in pharmacy for the study of polymorphism
Crystals, 2020Co-Authors: Zvonko Trontelj, Tomaž Apih, Janez Lužnik, Janez Pirnat, Vojko Jazbinšek, Zoran Lavrič, Stane Srcic, Veselko žagar, Samo Begus, J SeligerAbstract:Nuclear Quadrupole Resonance (NQR) spectroscopy has been known for 70 years. It is suitable for the study of measured (poly)crystalline chemical compounds containing Quadrupole nuclei (nuclei with spin I ≥ 1) where the characteristic NQR frequencies represent the fingerprints of these compounds. In several cases, 14N NQR can distinguish between the polymorphic crystalline phases of active pharmaceutical ingredients (APIs). In order to further stimulate 14N NQR studies, we review here several results of API polymorphism studies obtained in Ljubljana laboratories: (a) In sulfanilamide, a clear distinction between three known polymorphs (α, β, γ) was demonstrated. (b) In famotidine, the full spectra of all seven different nitrogen positions were measured; two polymorphs were distinguished. (c) In piroxicam, the 14N NQR data helped in confirming the new polymorphic form V. (d) The compaction pressure in the tablet production of paracetamol, which is connected with linewidth change, can be used to distinguish between producers of paracetamol. We established that paracetamol in the tablets of six different manufacturers can be identified by 14N NQR linewidth. (e) Finally, in order to get an extremely sensitive 14N NQR spectrometer, the optical detection of the 14N NQR signal is mentioned.
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Nuclear Quadrupole Resonance investigation of hydrogen bonding in some cocrystals of 2 3 5 6 tetramethylpyrazine and carboxylic acids
Journal of Physical Chemistry B, 2014Co-Authors: J Seliger, V. ŽagarAbstract:Cocrystals of 2,3,5,6-tetramethylpyrazine and several carboxylic acids have been prepared, and the complete 14N Nuclear Quadrupole Resonance spectra have been measured. The 14N Nuclear Quadrupole Resonance spectra have been used to check whether the cocrystals are indeed formed and to investigate the hydrogen bonding scheme of 2,3,5,6-tetramethylpyrazine molecules. Since a 2,3,5,6-tetramethylpyrazine molecule has two hydrogen bond acceptors, it may form either 1:1 or 1:2 cocrystals with carbocylic acids. 14N Nuclear Quadrupole Resonance is used to distinguish between these two possibilities. Rather large 14N Quadrupole coupling constants in the investigated cocrystals show that in these systems proton transfer O–H···N → O–···H–N+ does not occur. The Quadrupole coupling tensor in 2,3,5,6-tetramethylpyrazine cocrystals has been analyzed in terms of the deformation of the electron lone pair orbital and population of the π-electron orbital. The analysis shows that the two effects are correlated.
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14n Nuclear Quadrupole Resonance and proton spin lattice relaxation study of phase transition in pyridazine perchlorate
Solid State Communications, 2009Co-Authors: J Seliger, Veselko žagar, Tetsuo AsajiAbstract:Abstract The temperature dependence of the 14N Nuclear Quadrupole Resonance frequencies in pyridazine perchlorate has been measured by double Resonance. The results show that in the low temperature phase the pyridazinium ions are static, while in the high temperature phase the ions reorient around the normal to the plane of the ring between six equivalent orientations in agreement with the X-ray data. The 14N NQR data have been obtained for the protonated nitrogen position in the pyridazine ring for the first time. Temperature and frequency dependence of the proton spin–lattice relaxation time T 1 has been measured in both crystallographic phases. The results show the ionic mobility dominates T 1 in the low temperature phase. The activation energy for the ionic mobility is 240 meV. In the high temperature phase the pyridazine ring reorientation dominates the proton spin–lattice relaxation.
Y ōnuki - One of the best experts on this subject based on the ideXlab platform.
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73 ge Nuclear magnetic Resonance Nuclear Quadrupole Resonance investigation of magnetic properties of urhge
Journal of the Physical Society of Japan, 2015Co-Authors: Hisashi Kotegawa, Yoshinori Haga, Etsuji Yamamoto, Hisatomo Harima, Kenta Fukumoto, Toshihiro Toyama, Hideki Tou, Atsushi Harada, Y Kitaoka, Y ōnukiAbstract:We report on the 73Ge-Nuclear magnetic Resonance (NMR)/Nuclear Quadrupole Resonance (NQR) results for the ferromagnetic (FM) superconductor URhGe. The magnitude and direction of the internal field, Hint, and the parameters of the electric field gradient at the Ge site were determined experimentally. By using powdered polycrystalline samples oriented by different methods, the field dependences of NMR shift and Nuclear spin relaxation rates for H0 || c (easy axis) and H0 || b were obtained. From the NMR shifts for H0 || b, we confirmed a gradual suppression of the Curie temperature and observed a phase separation near the spin reorientation. The observation of the phase separation gives microscopic evidence that the spin reorientation under H0 || b is of first order at low temperatures. The Nuclear spin–lattice relaxation rate 1/T1 indicates that the magnetic fluctuations are suppressed for H0 || c, whereas the fluctuations remain strongly for H0 || b. The enhancements of both 1/T1T and the Nuclear spin–spi...
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strong coupling between antiferromagnetic and superconducting order parameters of cerhin 5 studied by i 115 n Nuclear Quadrupole Resonance spectroscopy
Physical Review B, 2009Co-Authors: M Yashima, Y Kitaoka, Y ōnuki, H Mukuda, H Shishido, Rikio SettaiAbstract:We report on a pressure $(P)$-induced evolution of magnetism and superconductivity (SC) in a helical magnet ${\text{CeRhIn}}_{5}$ with an incommensurate wave vector ${Q}_{i}=(\frac{1}{2},\frac{1}{2},0.297)$ through the $^{115}\text{I}\text{n}$ Nuclear Quadrupole Resonance (NQR) measurements under $P$. Systematic measurements of the $^{115}\text{I}\text{n}$-NQR spectrum reveal that the commensurate antiferromagnetism (AFM) with ${Q}_{c}=(\frac{1}{2},\frac{1}{2},\frac{1}{2})$ is realized above ${P}_{m}\ensuremath{\sim}1.7\text{ }\text{GPa}$. An important finding is that the size of SC gap and ${T}_{c}$ increase as the magnitude of the AFM moment decreases in the $P$ region, where SC uniformly coexists with the commensurate AFM. This result provides evidence of strong coupling between the commensurate AFM order parameter (OP) and SC OP.
David L. Bryce - One of the best experts on this subject based on the ideXlab platform.
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4 4 dipyridyl dioxide sbf3 cocrystal pnictogen bond prevails over halogen and hydrogen bonds in driving self assembly
Crystal Growth & Design, 2020Co-Authors: Patrick Scilabra, César Leroy, David L. Bryce, Giancarlo Terraneo, Andrea Daolio, Alberto Baggioli, Antonino Famulari, Giuseppe ResnatiAbstract:The SbF3·4,4′-dipyridyl N,N′-dioxide cocrystal is prepared and characterized via infrared spectroscopy and 121Sb and 123Sb Nuclear Quadrupole Resonance. Single crystal X-ray analysis proves that a ...
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121 123sb Nuclear Quadrupole Resonance spectroscopy characterization of non covalent pnictogen bonds and nqr crystallography
Journal of Physical Chemistry A, 2019Co-Authors: César Leroy, Ryan Johannson, David L. BryceAbstract:Pnictogen (or pnicogen) bonding is an attractive interaction between the electrophilic region of group 15 elements (N, P, As, Sb, Bi) and a nucleophile. This interaction for which unique applications in catalysis have recently been uncovered continues to gain popularity. Here, we investigate a series of pnictogen-bonded cocrystals based on SbF3 and SbCl3, prepared via mechanochemical ball milling, with 121/123Sb (I = 5/2 and 7/2, respectively) Nuclear Quadrupole Resonance (NQR) spectroscopy. Observed NQR frequency shifts upon cocrystallization are on the order of 0.1 to 10 MHz and are clearly diagnostic of the formation of pnictogen bonds to antimony. Further evidence for pnictogen bonding is obtained by complementary 13C cross-polarization magic-angle spinning solid-state NMR experiments. DFT calculations of NMR parameters as well as natural localized molecular orbital analyses support the experimental findings and elucidate the electronic origins of the experimental NQR frequency shifts. This work provi...
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121/123Sb Nuclear Quadrupole Resonance Spectroscopy: Characterization of Non-Covalent Pnictogen Bonds and NQR Crystallography
2019Co-Authors: César Leroy, Ryan Johannson, David L. BryceAbstract:Pnictogen (or pnicogen) bonding is an attractive interaction between the electrophilic region of group 15 elements (N, P, As, Sb, Bi) and a nucleophile. This interaction for which unique applications in catalysis have recently been uncovered continues to gain popularity. Here, we investigate a series of pnictogen-bonded cocrystals based on SbF3 and SbCl3, prepared via mechanochemical ball milling, with 121/123Sb (I = 5/2 and 7/2, respectively) Nuclear Quadrupole Resonance (NQR) spectroscopy. Observed NQR frequency shifts upon cocrystallization are on the order of 0.1 to 10 MHz and are clearly diagnostic of the formation of pnictogen bonds to antimony. Further evidence for pnictogen bonding is obtained by complementary 13C cross-polarization magic-angle spinning solid-state NMR experiments. DFT calculations of NMR parameters as well as natural localized molecular orbital analyses support the experimental findings and elucidate the electronic origins of the experimental NQR frequency shifts. This work provides insights into the changes in the antimony quadrupolar coupling constant upon pnictogen bonding: strikingly, the decreases noted here parallel those known for hydrogen bonds, but contrast with the increases reported for halogen bonds. The utility of the observed antimony Nuclear quadrupolar coupling constants in constraining structural models of cocrystals for which diffraction-based structures are unavailable, i.e., a rudimentary implementation of NQR crystallography, is established. Overall, this work offers a new approach to understand emerging classes of electrophilic interactions and to contextualize them in the broader landscape of established chemical bonding paradigms
Hisashi Kotegawa - One of the best experts on this subject based on the ideXlab platform.
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absence of magnetic dipolar phase transition and evolution of low energy excitations in prnb 2 al 20 with crystal electric field γ 3 ground state evidence from 93 nb nqr studies
Journal of the Physical Society of Japan, 2015Co-Authors: Tetsuro Kubo, Hisashi Kotegawa, Ryuji Higashinaka, Akihiro Nakama, Y Aoki, H SatoAbstract:We report measurements of bulk magnetic susceptibility and 93Nb Nuclear Quadrupole Resonance (NQR) in the Pr-based caged compound PrNb2Al20. By analyzing the magnetic susceptibility and magnetizati...
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73 ge Nuclear magnetic Resonance Nuclear Quadrupole Resonance investigation of magnetic properties of urhge
Journal of the Physical Society of Japan, 2015Co-Authors: Hisashi Kotegawa, Yoshinori Haga, Etsuji Yamamoto, Hisatomo Harima, Kenta Fukumoto, Toshihiro Toyama, Hideki Tou, Atsushi Harada, Y Kitaoka, Y ōnukiAbstract:We report on the 73Ge-Nuclear magnetic Resonance (NMR)/Nuclear Quadrupole Resonance (NQR) results for the ferromagnetic (FM) superconductor URhGe. The magnitude and direction of the internal field, Hint, and the parameters of the electric field gradient at the Ge site were determined experimentally. By using powdered polycrystalline samples oriented by different methods, the field dependences of NMR shift and Nuclear spin relaxation rates for H0 || c (easy axis) and H0 || b were obtained. From the NMR shifts for H0 || b, we confirmed a gradual suppression of the Curie temperature and observed a phase separation near the spin reorientation. The observation of the phase separation gives microscopic evidence that the spin reorientation under H0 || b is of first order at low temperatures. The Nuclear spin–lattice relaxation rate 1/T1 indicates that the magnetic fluctuations are suppressed for H0 || c, whereas the fluctuations remain strongly for H0 || b. The enhancements of both 1/T1T and the Nuclear spin–spi...
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detection of an unconventional superconducting phase in the vicinity of the strong first order magnetic transition in cras using as 75 Nuclear Quadrupole Resonance
Physical Review Letters, 2015Co-Authors: Hisashi Kotegawa, Hideki Tou, Shingo Nakahara, Rui Akamatsu, Hitoshi Sugawara, Hisatomo HarimaAbstract:Pressure-induced superconductivity was recently discovered in the binary helimagnet CrAs. We report the results of measurements of Nuclear Quadrupole Resonance for CrAs under pressure. In the vicinity of the critical pressure P(c) between the helimagnetic (HM) and paramagnetic (PM) phases, a phase separation is observed. The large internal field remaining in the phase-separated HM state indicates that the HM phase disappears through a strong first-order transition. This indicates the absence of a quantum critical point in CrAs; however, the Nuclear spin-lattice relaxation rate 1/T(1) reveals that substantial magnetic fluctuations are present in the PM state. The absence of a coherence effect in 1/T(1) in the superconducting state provides evidence that CrAs is the first Cr-based unconventional superconductor.
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connection between charge fluctuations and the coherent temperature in the heavy fermion system smos4sb12 a sb121 123 nqr study
Physical Review Letters, 2007Co-Authors: Hisashi Kotegawa, Hitoshi Sugawara, H Hidaka, Tatsuo C Kobayashi, Daisuke Kikuchi, H SatoAbstract:We report {121, 123}Sb Nuclear Quadrupole Resonance measurements under pressure in a novel heavy fermion (HF) system SmOs4Sb12. The Nuclear spin-spin relaxation rate 1/T{2} exhibits a distinct peak near the coherent temperature of the Kondo effect. The isotope effect of 121Sb and 123Sb indicates that the peak in 1/T{2} is electrical in origin. The connection between the peak in 1/T{2} and the development of coherency of the Kondo effect is robust even under pressure. It is conjectured that charge fluctuation plays an important role in forming the HF state in SmOs4Sb12.
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cooperative phenomenon of ferromagnetism and unconventional superconductivity in uge _2 a 73 ge nqr study under pressure
arXiv: Strongly Correlated Electrons, 2005Co-Authors: A. Harada, Yoshinori Haga, Shinji Kawasaki, Hisashi Kotegawa, Yoshio Kitaoka, Etsuji Yamamoto, Yoshichika Onuki, K. M. Itoh, Eugene E. Haller, Hisatomo HarimaAbstract:We report on a cooperative phenomenon of ferromagnetism and unconventional superconductivity (SC) in UGe$_2$ through the measurements of $^{73}$Ge Nuclear-Quadrupole-Resonance (NQR) under pressure ($P$). The NQR spectra evidenced phase separation into ferromagnetic and paramagnetic phases in the vicinity of $P_c\sim 1.5$ GPa, pointing to a first-order transition. The measurements of Nuclear-spin-lattice-relaxation-rate $1/T_1$ revealed that SC emerges under the background of ferromagnetism, but not of the paramagnetic phase.
Zvonko Trontelj - One of the best experts on this subject based on the ideXlab platform.
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Nuclear Quadrupole Resonance nqr a useful spectroscopic tool in pharmacy for the study of polymorphism
Crystals, 2020Co-Authors: Zvonko Trontelj, Tomaž Apih, Janez Lužnik, Janez Pirnat, Vojko Jazbinšek, Zoran Lavrič, Stane Srcic, Veselko žagar, Samo Begus, J SeligerAbstract:Nuclear Quadrupole Resonance (NQR) spectroscopy has been known for 70 years. It is suitable for the study of measured (poly)crystalline chemical compounds containing Quadrupole nuclei (nuclei with spin I ≥ 1) where the characteristic NQR frequencies represent the fingerprints of these compounds. In several cases, 14N NQR can distinguish between the polymorphic crystalline phases of active pharmaceutical ingredients (APIs). In order to further stimulate 14N NQR studies, we review here several results of API polymorphism studies obtained in Ljubljana laboratories: (a) In sulfanilamide, a clear distinction between three known polymorphs (α, β, γ) was demonstrated. (b) In famotidine, the full spectra of all seven different nitrogen positions were measured; two polymorphs were distinguished. (c) In piroxicam, the 14N NQR data helped in confirming the new polymorphic form V. (d) The compaction pressure in the tablet production of paracetamol, which is connected with linewidth change, can be used to distinguish between producers of paracetamol. We established that paracetamol in the tablets of six different manufacturers can be identified by 14N NQR linewidth. (e) Finally, in order to get an extremely sensitive 14N NQR spectrometer, the optical detection of the 14N NQR signal is mentioned.
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The Influence of Pressure in Paracetamol Tablet Compaction on ^14N Nuclear Quadrupole Resonance Signal
Applied Magnetic Resonance, 2013Co-Authors: Janez Lužnik, Janez Pirnat, Vojko Jazbinšek, Zoran Lavrič, Stane Srcic, Zvonko TronteljAbstract:^14N Nuclear Quadrupole Resonance (^14N NQR) of several commercially available paracetamol tablets was measured. The spectra of two polymorphs are presented. The linewidths of the correspondent ^14N NQR lines in all the measured samples containing the room-temperature stable monoclinic polymorph were noticeably different. We proved experimentally that the linewidth differences are the consequence of different compacting pressure in the production of tablets.
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polarization enhanced single shot n14 Nuclear Quadrupole Resonance detection of trinitrotoluene at room temperature
Applied Physics Letters, 2006Co-Authors: Janez Lužnik, Janez Seliger, Tomaž Apih, Robert Blinc, A Gregorovic, Janez Pirnat, Vojko Jazbinšek, Zvonko TronteljAbstract:The authors show that a combination of proton-nitrogen level crossing polarization transfer with a pulsed spin-locking sequence makes N14 Nuclear Quadrupole Resonance (NQR) fast and sensitive enough to be used in routine explosive detection as well as in the pharmaceutical industry for nondestructive chemical analysis of solid samples and polymorph determination. As an example we present “single shot” measurements of the N14 NQR spectra of 15g of trinitrotoluene at room temperature with a total measuring time of 20s.
